Mobile machine tool

ABSTRACT

A mobile machine tool, namely a manually-operated machine tool (10) or semi-stationary machine tool (10), for machining a workpiece (W), wherein the machine tool (10) has a plate-like guide element (30) with a guide surface (32) for guiding the machine tool (10) on the workpiece (W) or the workpiece (W) on the machine tool (10), wherein the machine tool (10) has a drive unit (11) with a drive motor (13) for driving a tool holder (14) arranged on the drive unit (11), wherein the machine tool (10) is provided with a tool sensor arrangement (61, 62) for detecting a workpiece contact region in which a work tool (15) arranged on the tool holder (14), is in contact with the workpiece (W). The tool sensor arrangement (61, 62) comprises at least two tool sensors (61, 62), the detection ranges of which (EB1, EB2) are assigned to different partial workpiece contact regions (WK1, WK2) of the workpiece contact region.

The invention relates to a mobile machine tool, namely amanually-operated machine tool or semi-stationary machine tool, formachining a workpiece, wherein the machine tool has an in particularplate-like guide element with a guide surface for guiding the machinetool on the workpiece or the workpiece on the machine tool, wherein themachine tool has a drive unit with a drive motor for driving a toolholder arranged on the drive unit, wherein the machine tool is providedwith a tool sensor arrangement for detecting a workpiece contact regionin which the work tool arranged on the tool holder, in particular acutting tool, is in contact with the workpiece, in particular cuttinginto the workpiece.

Such a machine tool is for example described in EP 1 980 363 A1. It isthus known for a workpiece contact region in which the work tool cutsinto or penetrates the workpiece to be displayed by means of a displaydevice in a manner convenient for the operator, so that they can alsoview the workpiece contact region conveniently if this for exampleconcealed by a cover.

However, the view of the workpiece and of the work tool is not optimal.

The object of the present invention is therefore to provide a machinetool with improved monitoring of the workpiece contact region.

In order to achieve this object, in a machine tool of the aforementionedtype the tool sensor arrangement comprises at least two tool sensors,the detection ranges of which are assigned to different partialworkpiece contact regions of the workpiece contact region.

Advantageously, the work tool engages at least partially between thedetection ranges of the tool sensors, so that the detection range of onetool sensor assigned to the partial workpiece contact region is at leastpartially obstructed by the work tool so as to prevent registration bythe other tool sensor.

Advantageously, in the machine tool or a machine tool of theaforementioned type, the tool sensor arrangement comprises at least twotool sensors for detecting a respective partial workpiece contact regionof the workpiece contact region on opposite sides of the work tool,wherein a section of the work tool engages in the workpiece in eachpartial workpiece contact region.

The two tool sensors (several tool sensors can also be provided) thus ineach case cover partial workpiece contact regions. The partial workpiececontact regions optimally lie within the detection ranges of therespective tool sensors, which allows a significantly improved view ofthe workpiece contact region. However, a “view of the workpiece contactregion” should not be understood to the effect that only a camera or anoptical sensor can be used. Other measuring principles for the toolsensors are also advantageous at this point, for example capacitive,inductive or similar measuring principles or detection principles, inparticular ones which work or function in a contact-free manner.

It is preferred if the detection ranges are assigned to opposite sidesof the work tool. Thus, each tool sensor covers the respective partialworkpiece contact region on one side of the work tool.

The partial workpiece contact regions of the workpiece contact regionare expediently provided on opposite sides of the work tool.

The partial workpiece contact regions on opposite sides of the work toolare for example wholly or partially obstructed by the work tool, so thatthe partial workpiece contact region which is assigned to one toolsensor is not covered, or is only partially covered by the other toolsensor.

It is further possible that the machine tool has several, i.e. more thantwo, tool sensors for detecting a respective partial workpiece contactregion. The tool sensors are preferably arranged in a row next to oneanother. It is for example possible that two tool sensors are assignedto opposite sides of the work tool or cover partial workpiece contactregions located there and the detection range of a third or further toolsensor lies between the detection ranges of the two aforementioned toolsensors.

Expediently, the machine tool has at least three tool sensors which arearranged in a row arrangement which runs, in the geometry of an outercircumferential contour of the work tool, around its outercircumferential contour. It is thus possible that the tool sensors arefor example arranged in a row next to one another around an outercircumference of the work tool. An arrangement of the tool sensors in arow expediently correlates with an outer circumferential contour orexpediently corresponds to an outer circumferential contour of the worktool. For example, in the case of a straight-line work tool the toolsensors can be arranged in a row arrangement along a straight line. Inthe case of a curved or arc-formed work tool the sensors are arrangedalong a curved or arc-formed row.

This means that each tool sensor can optimally cover the partialworkpiece contact region in each case assigned to it. For example, a rowarrangement of three or more tool sensors can be provided on the outercircumference of a milling tool.

According to an advantageous measure, one partial workpiece contactregion corresponds to an entry region of the work tool in the workpieceand the other workpiece contact region corresponds to an exit region ofthe work tool from the workpiece. Such an arrangement is in particularadvantageous in the case of plunge saws or other similar machine toolsthe work tool of which penetrates into the workpiece from above, so tospeak, wherein the outer circumference of the work tool engaging in eachcase with the workpiece surface of the workpiece increases withincreasing penetration depth of the work tool into the workpiece. Theoperator can thus monitor both regions, the entry region and the exitregion, optimally.

Expediently, the tool holder is mounted adjustably relative to the guidesurface in order to adjust a penetration depth of the work tool in theworkpiece, and the tool sensors are arranged in the region of a greatestdistance of the partial workpiece contact regions at the maximumpenetration depth of the work tool in the workpiece. Thus, there is asufficient distance between the tool sensors so that the work tool fitswithin the intervening space between the tool sensors at maximumpenetration depth in the workpiece. This means that the tool sensors arefor example arranged in the region of a maximum radial outercircumference of the work tool.

It is conceivable that at least one tool sensor is arranged on a side ofthe guide element facing the guide surface. For example, a jib or armcan project from the guide element from the direction of the work unitand so to speak cover the side of the guide element facing away from thedrive unit.

However, it is advantageous if at least one tool sensor, preferably bothor all tool sensors, are arranged on a side of the guide element facingaway from the guide surface. In other words, the tool sensors or the atleast one tool sensor are arranged on the side of the guide elementassigned to the drive unit. Thus, the guide surface is so to speak freeof tool sensors, which facilitates the handling of the machine tool. Theguide surface is freely accessible for the workpiece.

It is further advantageous if at least one tool sensor, preferably bothor all tool sensors, are arranged in a dust extraction region and/orbeneath a cover. It is further advantageous for the one or more toolsensors if they are arranged beneath a cover. In this way the toolsensors are protected. In particular, the dust extraction region is as arule provided in the vicinity of the work tool, so that the tool sensorscan in each case cover their assigned partial workpiece contact regiondirectly on the spot, namely in the vicinity of the work tool.

According to an advantageous measure, the machine tool is provided withan illumination device for illuminating the workpiece contact region.The illumination device comprises for example an LED arrangement orother illumination device.

In this connection it is preferable if, for each partial workpiececontact region, the illumination device has an illumination element forindividual illumination of the respective partial workpiece contactregion. In this way, an optimal local illumination is guaranteed, sincethe illuminating effect of the one illumination element can be matchedoptimally to the partial workpiece contact region or the detection rangeof the respective tool sensor, for example in terms of light colour,wavelength, intensity of illumination or the like. The work tool canalso obstruct or shade the light emitted by an illumination elementtowards the detection range of another tool sensor.

According to a preferred variant, the machine tool is provided with adisplay device, for example a screen, for displaying sensor signals fromthe tool sensors. For example, the sensor signals can comprise an imageinformation representing the respective partial workpiece contact regionwhich can be displayed by the display device.

According to a preferred concept, the machine tool is provided with aswitching device for switching between the sensor signals of the toolsensors, wherein the switchover device outputs the sensor signal of onetool sensor or the sensor signal of the other tool sensor as outputsignal in priority over the in each case other sensor signal dependingon at least one switching condition. The switchover device can forexample be part of the display or the display device. The switchoverdevice can also be formed by an evaluation device for evaluating thesensor signals or can be at least partially realised in this manner.

The at least one switching condition comprises for example a timecondition. For example, the sensor signal of one tool sensor can beoutput for a predetermined first time interval and then the sensorsignal of the other tool sensor can be output, for example as imageinformation on the display device. For example, on switching on themachine tool the sensor signal of the rear tool sensor, viewed in theworking direction, is output first, so that the operator has time toposition the work tool relative to the workpiece, for example in orderto lower a saw blade into the workpiece. Following expiry of thepredetermined first time interval, the switchover device so to speakswitches over to the image information or to the other sensor signal ofthe front tool sensor, viewed in the working direction. In this way theoperator can, for example in the case of an advance of the machine toolalong the workpiece in the working direction or of the workpiece alongthe machine tool in the working direction, monitor the respectivecutting region of the work tool or engagement region of the work tool inthe workpiece.

However, the machine tool can also be provided with a manually operableoperating element, for example a button, which can be operated by anoperator. The operating element generates a switching signal which isevaluated by the switchover device in order to switch between the sensorsignals from the tool sensors.

It should be pointed out at this point that a prioritised output of asensor signal does not mean that the other sensor signal is not output.For example, the sensor signal from one tool sensor can be output as alarger image on the display device than the sensor signal from the othertool sensor.

It is further advantageous if the switching condition comprises or isformed by an acceleration signal. For example, a forwards movement or amovement of the machine tool along the working direction is detected asan acceleration. It is also possible that a plunging movement of thedrive unit relative to the guide element or relative to the workpiece isinterpreted as an acceleration signal. For example, in the case of theaforementioned plunging movement the plunging movement per se can bedetected by the acceleration sensor. Depending on an accelerationsignal, for example the acceleration signal from this accelerationsensor, the display device can for example first display the sensorsignal of the rear tool sensor, viewed in the working direction. If nofurther acceleration towards the workpiece is then detected by theacceleration sensor, the plunging operation is completed. The displaydevice then switches over for example to the sensor signal from thefront tool sensor, viewed in the working direction.

According to a preferred concept, at least one tool sensor, expedientlythe tool sensor or both tool sensors, is or are arranged on the guideelement. This means that the tool sensors are for example positionedvery close to the partial workpiece contact regions.

It is preferred if the detection ranges of the tool sensors and/oroptical axes of the tool sensors are arranged at different anglesrelative to an outer circumference of the work tool. For example, onetool sensor covers the work tool or its outer circumference at a steeperangle than the other tool sensor. A steeper angle makes possible a moreprecise edge detection. A shallower angle makes it possible for examplethat a larger region of the workpiece next to the work tool still fallswithin the detection range of the tool sensor.

It is also expedient if the detection ranges of the tool sensors havedifferent detection angles, for example detection angles which differ by20-50%. For example, a front tool sensor, viewed in the workingdirection, can be equipped with a wide-angle lens or a wide-angledetection range, whereas in comparison the other rear tool sensor,viewed in the working direction, has a narrower detection angle.However, the detection angle of one tool sensor can differ even moremarkedly from the detection angle of the other tool sensor, for exampleby at least 80%, particularly preferably by at least 100% or around200%, in particular 200% to 300%. It can thus be seen that one toolsensor is so to speak a tool sensor with normal detection range, whereasthe other tool sensor can be a type of wide-angle tool sensor.

Preferably, the drive unit is, by means of a bearing arrangement,mounted adjustably on the guide element in order to adjust at least twoadjustment positions of the tool holder relative to the guide surface,wherein at least one adjustment position corresponds to a workpiecemachining position in which the work tool arranged on the tool holderis, in a workpiece contact region, in contact with the workpiece, inparticular cutting into the workpiece.

Advantageously, the machine tool has at least one tool sensor fordetecting the workpiece contact region and at least one position sensor,separate from the tool sensor, for detecting a relative position of thedrive unit relative to the guide element, and the machine tool has anevaluation device for evaluating sensor signals of the position sensorand of the tool sensor.

The relative position detectable by the position sensor can be anadjusted or adjustable relative position of the drive unit relative tothe guide element. The relative position can be an actual relativeposition, that is to say a current position of the drive unit relativeto the guide element, or a target relative position, for example arelative position, adjustable by means of a stop, which the drive unitassumes relative to the guide element on coming to rest against thestop.

The position sensor can comprise one or more position sensors. The samenaturally applies to the tool sensor, which can comprise one or moretool sensors. One could also describe the position sensor according tothe claims as “at least one position sensor” and the tool sensor as “atleast one tool sensor”.

The basic concept of the machine tool assumes that on the one hand theworking region can be scanned directly with a tool sensor, for examplein order to enable simple handling by the operator, in order todetermine a position of the work tool or the like. In this way theoperator can for example recognise if, and where, the work tool engageswith the workpiece. A further sensor, namely the position sensor, candetermine the relative position of the work unit relative to the guideelement, so that for example a current and/or adjusted working depth orpenetration depth of the work tool within the workpiece can bemonitored. For example it is possible that the position sensor displays,on a scale provided on a display of the machine tool, the respectiverelative position of the drive unit and/or a so to speak futureadjustable relative position of the drive unit relative to the guideelement, and thus also the assigned adjustment position of the driveunit and of the work tool relative to the workpiece.

The evaluation device preferably has an optical display device, inparticular a screen, an LCD display, an LED display or the like, fordisplaying at least one piece of optical information which is or can begenerated on the basis of a sensor signal of the position sensor and/orof a sensor signal of the tool sensor. Thus, if it includes a camera thetool sensor can also for example display an image of the workpiececontact region on the optical display device. The position sensor canfor example generate a position signal which is superimposed in thedisplay device or displayed by the display device as a marking, lightsignal, scale display or the like.

In one case the optical display device comprises individual lightsignals, for example LEDs or the like. Lightbars or rows of lamps, inparticular LEDs, are also readily possible. A comfortable display is forexample achieved through an LCD display. It is also advantageous if agraphic display is provided as display device or if the display devicecomprises a graphic display, so that for example a real image of theworkpiece contact region can be displayed on the display device.

The optical information which can be displayed on the optical displaydevice comprises for example an adjustment position information fordisplaying an adjustment position of the drive unit relative to theguide element and/or relative to the workpiece. The evaluation devicegenerates the adjustment position information on the basis of a positionsignal of the position sensor. The adjustment position information canfor example comprise or be formed by a linear representation, a pointrepresentation or the like. However, the adjustment position informationcan also be or comprise a scale display or dimension display. Forexample, the relative position of the drive unit in relation to theguide surface or to the surface of the workpiece is signalled throughthe adjustment position information. This allows the operator torecognise for example how far the work tool has already penetrated intothe workpiece, for example in the case of a separating cut, milling orthe like.

The adjustment position information is expediently an adjusted actualrelative position of the drive unit relative to the guide element. If,then, the position of the drive unit is adjusted relative to the guideelement, this is represented through the actual relative position or theadjustment position information. However, it is also possible that theadjustment position information comprises a target relative positionwhich can be set through an adjustment of the drive unit relative to theguide element. For example, a stop position or a predetermined orpredeterminable target adjustment position which the drive unit issupposed to assume relative to the guide element can be displayedthrough the adjustment position information.

According to an advantageous embodiment of the invention it can namelybe the case that the target adjustment position of the drive unitrelative to the guide element can be predetermined through a stop whichis or can be fixed in relation to the guide element. If the drive unitis adjusted relative to the guide element, it for example comes to restagainst the stop, wherein the target adjustment position of the driveunit predetermined through the stop is displayed on the display deviceas adjustment position information. The stop can be fixed, i.e. it canfor example be formed by a projection or a surface on the guide element.However, it is also possible that the stop is adjustable relative to theguide element, for example in order to adjust a penetration depth orworking depth of the work tool within the workpiece.

The optical display device is expediently configured to display aworkpiece marking arranged on the workpiece and/or to reproduce imageinformation captured by the tool sensor depicting the workpiece contactregion. For example, the workpiece marking, in particular a line orother optical marking on the workpiece, can be detected by the toolsensor, wherein this is displayed on the display device. However, asalready mentioned, the workpiece contact region can also be imaged orcaptured by the tool sensor and output as image information, wherein theimage information is made visible to the operator by the display device.

The image information relating to the workpiece contact region and/orthe marking on the workpiece is expediently displayed on the displaydevice synoptically with the aforementioned adjustment positioninformation.

Preferred is a calibration of the position sensor and/or its positionsignal:

Expediently, the evaluation device comprises a calibration means forcalibrating a position signal determined by the position sensor withreference to an actual tool position signal determined by the toolsensor. The position sensor or its position signal can also becalibrated with reference to the actual tool position signal. Theposition sensor can for example output non-linear position values orposition signals which are so to speak calibrated with reference to theactual tool position signal and converted into linear values and/orvalues representing a respective adjustment position, for example adepth adjustment position, of the drive unit relative to the guideelement. The actual tool position signal comprises for example the realengagement region of the work tool in the workpiece, for example a sawcut, a separating cut or the like. It is also for example possible thatthe position signal is not linear and is linearised on the basis of theactual tool position signal. It is also possible that, for example dueto the movement kinematics of the drive unit relative to the guideelement, the position signal does not represent the actual insertiondepth or penetration depth of the work tool in the workpiece. If forexample the drive unit swivels around an axis relative to the guideelement and thus relative to the workpiece, the work tool describes forexample a circular path with a motion vector perpendicular to the guideplane and a motion vector parallel to the guide plane, the amounts ofwhich differ depending on the respective arc segment, which results indifferent effects for example on a front and/or rear machined edge ofthe work tool on cutting into or engaging with the workpiece.

The actual tool position signal can for example represent an edge regionof the work tool and/or a machined edge, in particular a cut edge, onthe workpiece formed through a machining of the workpiece by means ofthe work tool. Thus, a front or rear cut edge or machined edge, viewedin the working direction of the work tool, can for example be detectedby the tool sensor and represented by the actual tool position signal.

Advantageous measures are provided for the registration and/orprocessing of the actual tool position signal:

In order to determine the actual tool position signal the evaluationdevice expediently comprises at least one optical filter and/or adigital filter or uses such a filter. For example, a better actual toolposition signal can be determined through an optical filtering, agreyscale filtering, a polarisation filtering or the like. A digitalfiltering, in which for example blurring, vibrations or the like arefiltered out through software filters or the like, is expedient inconnection with the determination of the actual tool position signal.

According to a further advantageous measure, the calibration means isconfigured to generate assignment information.

The evaluation device is advantageously configured to determine aninformation relating to a machined edge on the workpiece, for example acut edge, which has been formed or is being formed through a machiningof the workpiece by means of the work tool on the basis of theassignment information and an adjustment position of the drive unitrelative to the guide element which has been or can be set on themachine tool. The assignment information comprises for example anassignment table, a mathematical assignment function or both. The set orsettable adjustment position of the drive unit relative to the guideelement is expediently detected or detectable by the position sensor.

The assignment information expediently serves to allow the evaluationdevice to use the adjustment position of the drive unit relative to theguide element, in particular as registered by means of the positionsensor, to determine an information relating to a machined edge on theworkpiece which is being formed or which has already been formed througha machining of the workpiece by means of the work tool. If for example astop represents an adjustable setting position of the drive unit, thisadjustment position is registered by the position sensor. The evaluationunit determines on the basis of the position signal and the assignmentinformation an information which corresponds to the machined edgeactually being formed on the workpiece, namely a target position. If theoperator adjusts the drive unit relative to the guide element up to theadjustment position which is predetermined by the stop, the work toolcuts into the workpiece as far as the target position determined and/ordisplayed in this way, so that the machined edge or cut edge is formed.The operator can also already recognise, with reference to theinformation which is preferably displayed on the display device, towhich depth and/or up to which location they will cut into theworkpiece.

However, it is also possible that the information determined on thebasis of the position signal and the assignment information representsan actual cut edge or machined edge already being formed during thecurrent machining of the workpiece. If therefore, for example whilemachining the workpiece, the tool sensor has no view, so to speak, ofthe workpiece contact region, i.e. because this is for example obscuredby safety elements, covers or the like, dust etc., the evaluation devicedetermines on the basis of the position signal and the assignmentinformation an information as to the actual location of the work tool inorder for example to display this information on the display device orotherwise use it for the further machining of the workpiece.

Precision is significantly increased through the above measures.Mechanical tolerances, for example in the assembly of the machine tool,in the bearing arrangement, in the installation of the position sensorand/or of the tool sensor, are so to speak bridged or compensated oreliminated. On the basis of the assignment information, the positionsignal can so to speak be interpreted as a position signal whichrepresents the actual adjustment position of the drive unit relative tothe guide element or an adjusted position, for example of a stop for thedrive unit.

The assignment information advantageously relates to at least twoassignment coordinates or assignment axes oriented at an angle to oneanother.

The assignment information is thus expediently multi-axial, inparticular in relation to two assignment axes oriented at an angle toone another, in particular at right angles to one another. For example,the tool sensor signal of the tool sensor contains image information orpixels which are provided in directions oriented at an angle to oneanother, for example an x-direction and a y-direction. Accordingly, theassignment information for the position signal relates both to oneassignment axis, for example the x-axis, as well as to the otherassignment axis, for example the y-axis, in particular to assignmentaxes oriented at right angles to one another. If for example the imageinformation of the tool sensor not does not align exactly with a workingdirection of the machine tool in relation to the workpiece in which theworkpiece can be guided along the machine tool or, conversely, themachine tool can be guided along the workpiece, an unequivocalassignment information for the position signal is nonetheless determinedthrough the assignment of the image information to an x- and ay-assignment axis or in any case two assignment axes oriented at anangle to one another.

Thus, the position signal can for example represent an adjusted workingedge, for example a front or rear working edge of the work tool relativeto the workpiece, exactly, for example precisely to within 0.1 to 0.5mm, wherein the precision is limited solely by the resolution of thetool sensor, for example its digital resolution, and the resolution ofthe display device or of the position sensor. Any mechanical toleranceswhich can arise in the machine tool, the work tool or the like are thuspractically eliminated. Regarding the mechanical tolerances which havealready been mentioned, it should also be pointed out that these can forexample also arise through wear on the work tool.

According to an expedient concept, the position sensor and the toolsensor embody two different physical measuring principles.

It is further advantageous if the tool sensor comprises or is formed bya camera and the position sensor is not a camera. However, it should bementioned at this point that both the position sensor and the toolsensor can be formed by cameras or comprise cameras. Also, both theposition sensor and the tool sensor could be formed not by cameras butfor example by optical sensors using different measuring principles,inductive sensors or the like, or could comprise such sensors.

According to a preferred concept, the machine tool is provided with anillumination device for illuminating the workpiece contact region. Bymeans of the illumination device, in particular an LED arrangement orthe like, the workpiece contact region is made readily visible, whichfacilitates or improves registration by the tool sensor.

It is preferred if at least one filter, in particular a polarisationfilter and/or a colour filter and/or a grey filter, is installed beforethe tool sensor. The tool sensor is in this case for example an opticalsensor, a camera or the like. Reflections can for example be filtered bymeans of a polarisation filter, in particular a linear polarisationfilter or a circular polarisation filter, so that the signal of the toolsensor is influenced less, or not at all, through reflections. A colourfilter can for example limit the colour spectrum detectable by the toolsensor so that colours which are not relevant, for example a colour of awood or the like, are filtered out from the outset. A grey filter, whichcan have a single grey scale value or also a grey gradient or denser andless translucent zones can so to speak mask out bright regions.

An advantageous illumination device illuminates the workpiece contactregion and/or the detection range of the tool sensor or the detectionranges of the tool sensors with a brightness which is preferably greaterthan a brightness of an environment of the machine tool. For example, anillumination with a brightness which is typically not exceeded inworking areas is possible. In this way, an interfering influence ofambient light can for example be minimised or avoided, which improvesthe detection quality of the tool sensor.

In an advantageous illumination device, the brightness can beadjustable. This is for example possible by means of an adjustingelement or a graphic user interface provided on the machine tool.However, an automatic brightness adaption is also advantageous, i.e. themachine tool has at least one brightness sensor, in particularregistering an ambient light around the machine tool, and is configuredto adjust a brightness of the illumination device depending on thebrightness of the environment of the machine tool.

The tool sensor and/or the position sensor can comprise or be formed bydifferent sensors or measuring principles. The following are named byway of example, whereby combinations of these sensors or measuringprinciples are readily possible in the tool sensor and in the positionsensor:

A camera, an inductive sensor, a capacitive sensor, an optical sensor, atilt sensor, an acceleration sensor, a distance sensor, an electricalmeasuring resistor or the like.

For example, an electrical measuring resistor can be provided on a guideof the drive unit relative to the guide element. An optical sensor, forexample a sensor with a laser, a photocell or the like, can be providedto register the position. A tilt sensor which can for example detect atilt or swivel of the drive unit relative to the guide element is alsoadvantageous. By means of inductive measuring principles or capacitivemeasuring principles it is possible to detect for example a position ofthe work tool relative to the guide element.

It is advantageous if at least one position sensor is provided on thebearing arrangement.

The position sensor comprises for example a position sensor arranged onan angle adjustment device for adjusting an angular position of the workunit relative to the guide element. For example, a position sensor canbe provided on an angular guide or the like.

It is further advantageous if the position sensor comprises or is formedby a position sensor arranged on a depth adjustment device for adjustinga penetration depth of the work tool in the workpiece. For example, theposition sensor can detect the position of a stop which is mountedmoveably on the depth adjustment device.

It is further advantageous if the position sensor comprises a positionsensor arranged on a guide device, for example a linear guide, a swivelguide, an arc guide or the like, wherein the guide is provided in orderto guide the drive unit relative to the guide element.

It is also possible to provide a position sensor on a swivel bearing orsliding bearing of the bearing arrangement.

Naturally, several of the aforementioned position sensors can beprovided, for example a position sensor on the guide device and aposition sensor on the bearing arrangement.

Preferably, the machine tool is provided with a depth adjustment devicefor adjusting a penetration depth of the work tool in the workpiece. Thedepth adjustment device comprises a mounting contour which is arrangedon the guide element. A stop element is mounted moveably on the mountingcontour and/or can be fixed in a setting position assigned to arespective adjustment position of the tool holder relative to the guidesurface/to the workpiece or the workpiece surface. The drive unit comesto rest against the stop element in the respective setting position. Inthis way, the operator can also set a desired penetration depth ormachining depth of the work tool in the workpiece by means of the depthadjustment device. Such a depth adjustment device is for examplesuitable in order to adjust a target adjustment position of the driveunit relative to the guide element.

It is preferred if the position sensor comprises or is formed by aposition sensor for detecting the setting position of the stop elementin relation to the mounting contour. For example, an electricalmeasuring resistor is arranged on the mounting contour which can detectthe position of the stop element. However, an optical principle by meansof which the stop element can be detected, or the position of the stopelement relative to the mounting contour and thus the guide element, isalso expedient. Other measuring principles, for example inductive,capacitive or other measuring principles are also readily possible inthe position sensor which detects the stop element or its position.

The evaluation device is expediently configured to actuate the drivemotor and/or an actuating drive in order to adjust the drive unitrelative to the guide element depending on a sensor signal of the atleast one position sensor and/or of the tool sensor. For example, thedrive motor can be shut off automatically or the drive unit adjustedautomatically if a respective target adjustment position is reached.However, it is also readily possible that the aforementioned opticaldisplay device is provided in this embodiment too, i.e. that theoperator can see what the machine is doing automatically, for example bymeans of the optical display device, or that the operator can switch themachine over from an automatic mode in which the evaluation devicecontrols the drive motor or the actuating drive into a manual mode inwhich they machine the workpiece so to speak with reference to theoptical display device. For example, the evaluation device can shut offthe drive motor if a saw cut or another workpiece machining operation iscompleted. It is also possible that the evaluation device controls theactuating drive such that for example the work tool is moved away fromthe workpiece or towards the workpiece.

It is preferred if the machine tool is provided with not just one toolsensor but several, in particular at least two tool sensors.

Preferably, a tool sensor arrangement is provided which comprises atleast two tool sensors, each covering a respective partial workpiececontact region of the workpiece contact region on opposite sides of thework tool. A section of the work tool engages in the workpiece in eachpartial workpiece contact region. For example, a front side, viewed inthe working direction, and a rear side, viewed in the working direction,of the work tool can in each case be covered by a tool sensor. Theaforementioned assignment information or the like can in this way bedetermined significantly more precisely because for example therespective penetration depth of the work tool in the workpiece can bedetected not just by one tool sensor but by several tool sensors.

It is namely advantageous if the evaluation device is provided with acalibration means, in particular the calibration means mentioned andexplained above, for calibrating a position signal determined by theposition sensor on the basis of workpiece actual position signalsdetermined through tool sensors assigned to the partial workpiececontact regions of the workpiece contact region. This allows asignificantly greater precision to be achieved.

It is further advantageous if the machine tool, for example theevaluation device, is configured to determine a positioning of the guideelement on a guide device, for example a guide rail, for guiding theguide element. The guide element can for example be guided or guidableon the guide device or guide rail in a straight line in a workingdirection. A machining depth or penetration depth of the work tool inthe workpiece depends on whether the guide element is arranged on theguide device or next to the guide device. For example, in order toachieve the same penetration depth or machining depth of the work toolin the workpiece, the drive unit needs to be swivelled further in thedirection of the guide element if the guide element rests on the guiderail/guide device and not directly on the workpiece. The evaluationdevice can for example perform the aforementioned calibration,assignment of position signals and image signals on the display devicesor the like depending on a positioning of the guide element on the guidedevice or next to it, for example directly on the workpiece. In thisway, the respective height of the guide rail or guide device, i.e. thedistance from the upper side of the guide device to its undersideresting on the workpiece, is so to speak automatically included in thecalibration, assignment of signals and the like by the machine tool.

However, different sensor concepts or image processing concepts can beused to detect a guide rail, for example the relation of an edge of themachine tool to the workpiece and/or the guide rail. A guide rail canalso for example be identified on the basis of unique opticalcharacteristics, for example its straight longitudinal extension, itscolour, its patterning or by means of a unique identifier, for example abit pattern or line code. Finally, an image comparison or templatecomparison is also possible in which the image of the guide railcaptured by the tool sensor is compared with a comparison image.

It is preferred if a tool sensor or all tool sensors of the machine toolare arranged at a distance from the guide surface. For example, thedrive unit extends away from the guide surface to a maximum height. Themaximum height is for example defined by an upper side of a machinehousing of the drive unit, whereas the guide surface so to speakrepresents the underside of the machine tool. The tool sensor ispreferably arranged on the machine tool at a distance from the guidesurface which amounts to at least 20%, preferably 30%, in particular 40%or 50% of a maximum height by which the drive unit extends away from theguide surface.

It is possible that the detection range of at least one tool sensor maybe at least partially affected by particles which are produced duringthe machining of a workpiece by means of the work tool. In this case itis advantageous if the machine tool is provided with at least oneoptimisation means to reduce the effect of the particles present withinthe detection range on a tool sensor signal of the tool sensor.

The tool sensor signal can be the output signal of the tool sensor or asignal generated or generatable on the basis of an output signal of thetool sensor. The output signal of the tool sensor is thus alreadyimproved by means of the optimisation means in order to generate thetool sensor signal.

It is thus a fundamental concept of the one or more optimisation meansthat the particles which are in any case unavoidable within thedetection range, for example chips, dust or the like, are so to speakoptically eliminated, or their effect on the tool sensor signal reduced,by means of the at least one optimisation means. Naturally, this doesnot rule out the possibility that further measures for enhancing theimage quality are also provided, so that for example purge air reducesthe entry of particles into the detection range of the tool sensor orflushes away particles which are present there as optimally as possible.For example, a purge air flow in the form of a suction flow or coolingair flow can be provided which so to speak flushes the particles out ofthe detection range. It is in particular possible that the detectionrange of the tool sensor is flowed through by purge air, for example bya suction flow and/or a cooling air flow of the drive motor.

However, the at least one optimisation means is expediently a separatemeans from the purge air, for example a suction flow or cooling airflow.

The at least one optimisation means expediently comprises or is formedby a digital signal processing means, wherein the signal processingmeans is intended or configured to process or form the tool sensorsignal. For example, a signal which the tool sensor generates can bemodified or processed by the signal processing means in order to formthe tool sensor signal.

For example, the digital signal processing means comprises or is formedby at least one digital filter for filtering pixels generated by theparticles. The pixels are for example interference information which isfiltered out by the digital filter. The digital filter is for exampleformed by a program code which can be executed by a processor of themachine tool.

The digital signal processing means can expediently comprise a rankorder filter. However, a histogram filter, a brightness filter or thelike are also readily advantageous. It is possible that theaforementioned filters are combined with one another, i.e. a brightnessfilter is for example fitted, and then a rank order filter.

In the case of the rank order filter it is advantageous if it comprisesor is formed by a so-called median filter. If for example further imageinformation is collected within a defined vicinity of a pixel, anaverage grey value, i.e. a median, is selected from this sorted list,the interference pixel then being replaced with an average value, inparticular a grey value or colour value.

However, other filters, for example a Gauss filter and/or a bilateralfilter and/or an averaging filter, can also advantageously be provided.A Gauss filter is for example a so-called frequency filter, in which arespective step response contains no overshoot and at the same time amaximum edge steepness is achieved in the transition region. Thetransmission function and the pulse response have for example the formof a so-called Gaussian bell curve.

A bilateral filter is for example a non-linear filter which is used inorder to soften images while at the same time preserving object edges.An object edge can for example be a saw cut in the workpiece. However, asurface or edge of the work tool can also be filtered in this way.

A histogram filter or histogram equalisation is advantageous in orderfor example to achieve a more even or better brightness distribution.That is to say the signal from the tool sensor becomes more even interms of its brightness distribution and/or colour distribution as aresult of the histogram balancing.

A sliding coating is preferably provided on a front side or atransparent cover of the tool sensor, along which the particles slide orwhich the particles can slide off. The transparent cover is for exampleformed by a front lens of the tool sensor. A filter or a transparentplate can also be provided as transparent cover.

However, the at least one optimisation means can also comprise or beformed by an illumination device. In this way the detection range is soto speak deliberately brightened or illuminated by the illuminationdevice, which significantly improves the image registration.

In order to illuminate the detection range, the illumination device isexpediently arranged at an angle transverse to an optical axis of thetool sensor, in particular a camera. In particular, the illuminationdevice represents or forms the exclusive illumination of the detectionrange. Thus, the detection range is deliberately not illuminated in ornear to the optical axis of the tool sensor, so that interferingreflections occur, because in this case the particles would reflect backthe light from the illumination device so to speak along the opticalaxis or the detection axis of the tool sensor.

The aforementioned angles between the optical axis of the tool sensorand the light source are expediently formed in relation to at least oneplane, preferably to several planes. For example, the angles are formedin relation to a plane oriented parallel to the guide surface and/ororiented at an angle, for example a right angle, to the guide surface.

It is advantageous if this angle is at least 30°. Steeper angles, forexample 45°, at least 60° or the like, are however more advantageous. Anangle of for example around 80-120°, in particular around 90°, isparticularly favourable.

Accordingly, a central axis or light beam central axis is arranged at anangle of for example 30°, 40°, 60° or particularly preferably 80-90°.That is to say the detection range is so to speak illuminatedtransversely to the optical axis of the tool sensor.

It is expedient if the illumination device is designed to provide adiffuse illumination of the detection range. For example, theillumination device comprises one or more light sources arranged behinda diffusing lens, for example a Fresnel lens, a matte lens or the like.This prevents for example strong and/or localised reflections, forexample on the particles, a workpiece surface or components of themachine tool.

According to an advantageous concept, the illumination device isarranged so as to illuminate the detection range of the tool sensor fromopposite sides. For example, the illumination device has lamps onopposite sides of the detection range, in particular LEDs or the like.If illumination takes place from opposite sides, it is againadvantageous if an angle between the light beams or the main radiationaxes of a respective lamp and the optical axis of the tool sensor is atleast 30°, preferably at least 45°. It is particularly favourable if themain axes or beam axes of the lamps or the illumination device arearranged at an angle of around 80-120°, in particular around 90°, to theoptical axis of the tool sensor. The illumination from opposite or bothsides, for example at right angles to the saw blade or other work tool,prevents or in any case reduces cast or hard shadows.

It is further advantageous if the machine tool is provided with anenclosure device to shield the detection range from extraneous lightinfluences. In this way the detection range is so to speak protectedagainst extraneous light influences. If the aforementioned illuminationdevice is arranged within the detection range, a targeted illuminationof the detection range is possible, so that an optimal matching of theillumination device and the tool sensor is possible. For example, aspecific light colour can be generated which can be detected optimallyby the tool sensor.

The enclosure device can be a so to speak dedicated enclosure devicecovering the detection range, for example a mask or the like. However,it is also possible that components of the machine tool which arenecessary in order to protect the work tool or for other measures, forexample a dust cover or the like, form a part of the enclosure device orrepresent the enclosure device as a whole.

If the machine tool is removed from the workpiece or the workpiece isremoved from the machine tool, the detection range can at leastpartially be exposed to extraneous light. However, it is preferred ifthe enclosure device and the workpiece shield, or at least substantiallyshield, the detection range from extraneous light influences duringoperation of the machine tool. If the illumination device is thenactivated in the dark, covered region, so to speak, an optimal imagecapture and/or image evaluation is possible. For example, theaforementioned enclosure device can extend as far as the guide surfaceof the machine tool, an opening only being present in the region of theguide surface beyond which the work tool projects relative to the guidesurface in at least one operating mode or in one position of the driveunit relative to the guide surface.

The tool sensor can for example be arranged on a dusty air duct forextracting dusty air laden with particles from the machine tool. Forexample, the dusty air duct extends on the work tool and/or around thework tool.

Expediently, an airflow device, for example comprising one or more guidewalls or guide plates or the like, is provided in the region of the toolsensor. The airflow arrangement is configured and/or arranged such thatit deflects a particle flow containing particles away from the toolsensor.

The tool sensor expediently comprises or is formed by a camera. However,other sensory principles are possible, for example measurement with anoptical sensor, capacitive sensor or the like. Here too, the particlescan cause a certain interference.

The detection range of the tool sensor expediently covers at least 45°,preferably at least 60°, particularly preferably at least 70°. The toolsensor comprises for example a wide-angle lens.

The tool sensor is preferably arranged very near to the work tool, forexample at a distance of less than 5 cm, in particular less than 4 cm or3 cm. In this case, detection by means of a wide-angle lens isparticularly advantageous.

According to a per se independent concept, also advantageous inconnection with the above invention or a per se separate invention, themachine tool is provided with a soiling checking means for checking asoiling of the tool sensor by particles. The machine tool is equipped toprocess the tool sensor signal depending on a degree of soiling of thetool sensor and/or to output a warning, for example an optical oracoustic warning, depending on a degree of soiling of the tool sensor.For example, the soiling checking means generates a sensor signal oroutput signal which represents the degree of soiling. However, thesoiling checking means can also be realised through the image processingor signal processing device which processes signals from the tool sensorand provides the tool sensor signal. Thus, a brightness value of thetool sensor signal can for example be adjusted, in particular by meansof a histogram equalisation. If a predetermined or adjustable thresholdvalue for the brightness is exceeded, the machine tool issues a warning,for example on a screen, by means of an LED display, by means of asignal tone, via a loudspeaker or the like.

According to a preferred concept, the soiling checking means is designedto determine the degree of soiling of at least one brightness value inthe tool sensor signal and/or an output signal of the tool sensorprovided in order to determine the tool sensor signal.

It is preferred if the soiling checking means comprises at least onelight source, for example one or more light sources of theaforementioned illumination device or a separate light source, forilluminating a front side of the tool sensor, as well as at least onelight sensor to determine a reflection from the front side of the toolsensor depending on a soiling of the front side through particles. It isadvantageous if the front side of the tool sensor, for example a frontside of the lens, a filter element or the like, is illuminated by thelight source, for example by an LED.

The light source and the light sensor are expediently arranged in amanner corresponding to an angle of incidence and an angle of reflectionrelative to the front side of the tool sensor. The illuminationexpediently takes place below a total reflection. If, therefore, thelight sensor, for example a photodiode, registers the light reflected bythe front side of the tool sensor or the particles present thereon, inthe case of a front side soiled by particles for example, an increasedor reduced reflection can be registered by the light sensor as anindication or as a measure of the degree of soiling.

It is also possible that the illumination takes place in a colourspectrum which cannot be registered by the tool sensor or which does notinterfere with detection. For example, the light source generates lightwithin a non-visible range and/or an infrared range. Typical cameraswhich are advantageous as tool sensors can for example be unable todetect infrared light, so that the aforementioned brightness check bymeans of an infrared light source and a corresponding light sensor doesnot interfere with the coverage of the workpiece contact region.

A detection range of the tool sensor expediently comprises a workpiececontact region in which the work tool is in contact with the workpiece,for example a machined edge created, or being created, through themachining of the workpiece by means of the work tool, as well as a frontregion, viewed in a working direction. The machine tool can be guidedalong on the workpiece or the workpiece can be guided along on themachine tool in the working direction. For example, the work tool cutsinto in the workpiece in the working direction.

It is also expedient if the tool sensor is configured and/or aligned todetect a workpiece marking arranged on the workpiece. For example, thedetection range of the tool sensor is directed at a, viewed in theworking direction, foremost region of the workpiece or at a machiningregion which is, viewed in the working direction, located before thework tool.

The detection range of the tool sensor thus advantageously comprises, onthe one hand, the actual engagement region or contact region of the worktool with the workpiece, but in addition also the region in front ofthis, viewed in the working direction. This gives the operator anoptimal control over the working operation.

Furthermore, it is expedient if the machine tool or a machine toolaccording to the invention is configured to provide at least onefunction depending on a detection of a workpiece marking arranged on theworkpiece. For example, the evaluation device can be provided with anedge detection or line detection function which detects the workpiecemarking. The workpiece marking is for example a scribe line, a line orthe like.

The at least one function comprises for example the display of adistance of a current machined edge from the workpiece marking. Thedisplay takes place for example on a display device or on the displaydevice, so that the operator can control how far away from the workpiecemarking the current working edge of the work tool still is in relationto the workpiece.

However, an automatic concept is also possible in which the machine toolperforms motory, braking or actuatory functions depending on theworkpiece marking being reached. For example, the work tool can bebraked on reaching the workpiece marking. An anticipatory approach isthereby advantageous, i.e. such that the machine tool already causes thedrive unit to run more slowly, so to speak, if the machined edge islocated in the vicinity of the workpiece marking. Furthermore, anactuating drive of the machine tool can also be provided in order toadjust the drive unit relative to the guide unit, for example anactuating drive with which the drive unit is swivelled or slid relativeto the guide element. Depending on whether the workpiece marking hasbeen reached, the machine tool, for example the evaluation device,actuates a corresponding actuating drive. For example, the work tool canbe moved out of the workpiece by the actuating drive on reaching orbefore reaching the workpiece marking. Naturally it is advantageous ifthe function also comprises an actuation of the drive unit, for examplean adjustment of a rotational speed of the drive motor, on reaching theworkpiece marking.

It is preferred if the machine tool is provided with at least one toolsensor, in particular a camera, on a side of the work tool facing awayfrom the drive unit, in particular the drive motor. The tool sensor isfor example located on a free end face or flat side of the work tool.The work tool is so to speak arranged between the tool sensor and thedrive unit, in particular its drive motor. The tool sensor is forexample arranged on a cover on the enclosure of the work tool.

However, alternatively or in addition, an embodiment is also possiblewherein at least one tool sensor is provided on a side of the work toolfacing the drive unit, for example the drive motor. The tool sensor canthus for example be located in the dust extraction duct or in anotherposition.

It is also expedient if the at least one tool sensor is arranged abovethe guide surface and/or does not project laterally beyond the guidesurface. This means that the tool sensor is not in the way duringmachining of the workpiece. The tool sensor is thus located above aprojection of the guide surface, in particular in the region of thedrive unit.

It is possible that a tool sensor is fixed in relation to the guideelement, i.e. is arranged on the guide element. In particular, such atool sensor, for example a camera, is arranged in the region of alongitudinal side of the guide surface, so that its detection range isdirected at the workpiece contact region.

It is further advantageous if at least one tool sensor is arranged onthe drive unit, so that it follows movements of the drive unit relativeto the guide element, i.e. its detection range is so to speak adjustedalong with the drive unit.

The machine tool is advantageously provided with an evaluation devicefor evaluating a tool sensor signal generated by the tool sensor. Themachine tool has as tool sensor for example a camera, the image fromwhich is displayed on a display. The image on the display changesdepending on the arrangement and orientation of the camera. Thedisplayed image is thus to a great extent dependent on the orientationof the camera.

Advantageously, a reference marking which can be detected by the toolsensor is arranged within the detection range of the tool sensor and theevaluation device is configured to determine at least one correctionvalue for the tool sensor signal depending on the reference marking.

It is thereby a fundamental concept that the reference marking is so tospeak detected by the tool sensor itself and the evaluation device,which can also form a part of the tool sensor, determines at least onecorrection value with reference to the reference marking. With the atleast one correction value, the tool sensor signal can be correctedaccordingly, for example the orientation can be adjusted on the basis ofan output information generated by means of the tool sensor signal, forexample on an output device, for example a screen or a display. Thus, anorientation of an image of a workpiece contact region can for example bebrought into alignment with further components, for example a side edgeof the guide element. Thus, the operator can for example follow theprogress of work on the output device with reference to an image whichhas been oriented optimally in relation to the other components of themachine tool.

It is preferred if the reference marking comprises or is formed by aline or a pattern.

The reference marking expediently comprises a line or an arrangement oflines, a pattern or the like. Particularly advantageous is acheckerboard pattern. However, for example barcodes or other geometricalpatterns can also be used as reference marking. It is also possible thatthe reference marking comprises one or more points. For example, therelation between different reference points can be used by theevaluation device in order to determine the at least one correctionvalue.

It is further advantageous if the reference marking represents a uniquereference marking, for example a code.

The reference marking can for example be or comprise a QR code (QR=QuickResponse) or a comparable pattern.

It is particularly preferable if the at least one reference markingdiffers in terms of size and/or geometry and/or extent and/or colourand/or contrast from a functional component of the machine tool in thevicinity of the reference marking which does not fulfil the function ofthe reference marking. The functional component of the machine tool isfor example a section of the guide element or of the machine housing.For example, the reference marking has a different colour or a differentcolour spectrum from a wall surface on which it is arranged.

Advantageously, the reference marking has at least one colour and/or atleast one contrast which differs by a predetermined degree from atypical colour spectrum of an environment of the reference marking orwhich differs by a predetermined value from a typical contrast range ofan environment of the reference marking. For example, a colour distanceof at least one colour of the reference marking differs by apredetermined value from the colour temperature of the environment ofthe reference marking. A Euclidian distance amounts for example to atleast 0.5-1.0 between the colours of the reference marking and theenvironment, so that it is apparent to a practised eye. However, theEuclidian distance can also be greater, for example within a value rangeof 2-4. The light-dark contrasts of the environment of the referencemarking, for example a wall surface next to the reference marking,amount for example to 5 to 1 or 10 to 1, whereas the contrasts in thereference marking are higher, for example at least twice as great orthree times as great. This is for example the case with a checkerboardpattern or a QR code with white and black or dark grey areas.

It is particularly preferable if the reference marking comprises or isformed by a control marking, for example a control pattern, a linearrangement or the like, provided specially for the purpose ofdetermining the correction value. The control marking is for example ageometrical structure which is arranged on the machine tool exclusivelyor specially in order to determine the correction value. The controlmarking or the control pattern is for example designed or provided inthe form of a varnish, coating, foil or the like. The control markingpreferably serves as a reference marking exclusively for the purpose ofdetermining the correction value and otherwise has no function, forexample no mechanical supporting function or the purpose of limiting anopening.

However, it is also possible that one or more components which in anycase, so to speak, form part of the machine tool can be used asreference marking. For example, according to one variant of theinvention the reference marking is formed by at least one contour of atleast one mechanically functional component of the machine tool, forexample at least one contour of the work tool and/or of the guideelement, or comprises the at least one contour. A mechanicallyfunctional component of the machine tool is for example a drivecomponent, a guide component, a supporting structure or the like.Conversely, a purely optical marking, for example in the form of acoloured and/or structured surface, which is applied specially for thepurpose of determining the correction value, is not understood as amechanically functional component in this context.

For example, an edge of the work tool, of the guide element or the likecan form or comprise such a contour. If several machine parts are withinthe detection range, in particular the visual range, of the respectivetool sensor, these can, individually or as a whole, form the referencemarking. It is for example possible that an edge of the guide element,for example of a saw bench or workbench, and at the same time an edge ofthe work tool serve as reference marking(s).

According to a preferred concept, the evaluation device is configured toanalyse a curvature of a straight-line section of the reference markingin order to determine the at least one correction value. For example, astraight line can appear curved due to an optical distortion of the toolsensor or of a lens of the tool sensor. The evaluation device determinesdeviations from a straight line on the basis of the curvature values orgeometrical values of the curved, optically registered line of thereference marking in order then to correct the tool sensor signalaccordingly on the basis of these correction values or of the at leastone correction value. For example, image information contained in thetool sensor signal can, so to speak, be optically straightened on thebasis of the correction values which are derived from the curvature. Theevaluation device is thus for example equipped to rectify image signalswhich are contained in the tool sensor signal or in raw signals of thetool sensor. For example, the tool sensor signal which is processed ormodified by the evaluation device can, so to speak, be opticallyrectified.

According to a preferred concept, the tool sensor comprises or is formedby a camera. The camera is for example a digital camera.

It is further preferred if the tool sensor, in particular theaforementioned camera, is intrinsically calibrated. The intrinsiccalibration is preferably multi-axial, i.e. for example biaxial ortriaxial/spatial.

It is also advantageous if the tool sensor, in particular the camera, isextrinsically calibrated. The extrinsic calibration can also be abiaxial or triaxial or spatial calibration.

It is also possible that the evaluation device is equipped for intrinsiccalibration of the tool sensor. For example, an arrangement of one ormore control patterns can be provided on a background as a calibrationmeans, in particular forming a system component of the machine tool. Theevaluation device can for example capture several images of the controlpattern or the control patterns and in this way determine intrinsiccalibration values for the tool sensor, in particular the camera.

In the case of intrinsic calibration it is for example possible thatirregularities, curvatures or other similar optical errors are so tospeak equalised or balanced out through the calibration. The tool sensorcan thus supply corrected/calibrated values. It is also possible thatthe evaluation device corrects/calibrates the tool sensor signal so tospeak automatically on the basis of the values obtained through theintrinsic calibration, for example before the tool sensor signal isdisplayed on the display device.

The already intrinsically calibrated camera or the intrinsicallycalibrated tool sensor is then configured to achieve an optimalevaluation of the reference marking on the machine tool. By means of theintrinsically calibrated camera or the intrinsically calibrated toolsensor, the evaluation device can for example determine a relativealignment and/or orientation of the camera or of the tool sensor inrelation to the reference marking.

Preferable is a so-called extrinsic calibration of the at least one toolsensor in relation to the reference marking.

For example, the evaluation device can convert or transform an inparticular global, two-dimensional or three-dimensional coordinatesystem provided through the reference marking into a local coordinatesystem relating to the respective pose, i.e. the orientation andpositioning of the camera or of the tool sensor in space.

Preferably, the evaluation device is configured, by means of theintrinsically calibrated camera or the intrinsically calibrated toolsensor, to carry out a so-called extrinsic calibration, namely acalibration in relation to the at least one reference marking of themachine tool. Thus, an alignment and/or orientation of the test regionsby means of the reference marking can for example be realised throughthe evaluation device.

According to a preferred concept, the evaluation device is configured todetermine a test region within the detection range with reference to thereference marking. For example, a test region is determined withreference to the reference marking within which a cut edge or machinededge is formed which is created during the machining of the workpiece,depending on the work tool. Thus, within the detection range, which mayfor example be quite large, a smaller test region in comparison with thedetection range is determined which is used for a detailed evaluation.In this way, interference information located outside of the testregion, for example chips, light reflections or the like, can so tospeak be masked out. The evaluation device “concentrates”, so to speak,on the region essential for the evaluation, namely the test region.

The test region is thus determined or determinable independently of aninstallation position and/or orientation of the respective tool sensor.If for example a tool sensor, in particular a camera, is, in departurefrom an ideal installation position and/or orientation, mounted on themachine housing or in the machine housing or another component of themachine tool, the machine tool also determines the test region for thissuboptimal installation position and/or orientation of the tool sensor.Installation tolerances or tolerances of the tool sensor per se, forexample an installation position of a digital image sensor in relationto a camera axis or the like, are so to speak automatically compensated.

When the work tool is removed from the workpiece, the, or a, test regioncan for example be determined on the basis of a saw cut or othermachining contour. In this situation, an orientation of the test region,for example the course of a sawn edge or other machined edge, is forexample particularly simple to realise.

It is preferred if the evaluation device is configured to determine thetest region, or a test region, within the detection range of the toolsensor with reference to a machining contour on the workpiece created bythe work tool, for example a sawn edge, which runs in the workingdirection of the machine tool. Such a machining contour can readily bedetected, in particular by means of filtering, edge detection or thelike. The test region is for example oriented on the machining contour.The machining contour is for example created through a sort of testmachining of the workpiece, for example a saw cut, wherein the testmachining is only, or preferably, carried out for the purpose ofcalibration and/or orientation of the test region on the workpiece. Thearrangement and/or orientation and/or geometrical form of the machiningcontour depends for example on whether the machine tool is used with orwithout a guide rail or a guide device. Furthermore, the type andgeometry of the work tool, wear on the work tool or the guide device andthe like can for example have an effect on the machining contour. Suchinfluences on the machining contour are so to speak taken intoconsideration by the evaluation device if the machining contour is usedto determine the test regions.

Several test regions can readily be set up and/or stored in the machinetool or the evaluation device. For example, a test region with guiderail and a test region without guide rail can be determined ordeterminable.

According to a preferred concept, the machine tool, for example theevaluation device, is configured to orient an optical informationgenerated or generatable by means of the tool sensor signal relative tothe reference marking. For example, an optical information whichrepresents the contact region of the work tool with the workpiece can soto speak be oriented relative to the rest of the machine tool on thebasis of the at least one correction value.

Expediently, the machine tool is provided with a height measuring devicefor detecting a height of the workpiece, wherein the height correspondsto a distance between an upper side of the workpiece which is to bepenetrated by the work tool and an underside of the workpiece oppositethe upper side of the workpiece.

It is thereby a fundamental concept that the operator is so to speakable to achieve an optimal adjustment of the penetration depth of thework tool in the workpiece in that they receive information concerning aheight of the workpiece. The height measuring device is installed onboard the machine tool, which facilitates handling. Thus, the operatordoes not need to lay a yardstick or other measuring device against theworkpiece in order to determine its height. Operation is convenient.

A detection of a height of the workpiece is for example advantageous interms of achieving an optimal cut quality and/or an optimal dustextraction. Furthermore, lower machining forces, for example cuttingforces, are sufficient in the case of a machine tool which is optimallyadjusted in relation to the height of the workpiece.

The height measuring device is expediently configured to detect an upperworkpiece edge between an end face of the workpiece and the upper sideof the workpiece and/or to detect a lower workpiece edge between an endface of the workpiece and the underside of the workpiece. The end faceis preferably oriented at right angles to the upper side of theworkpiece and/or underside of the workpiece. It is advantageous if theheight measuring device can detect both workpiece edges, namely theupper and the lower workpiece edge, though this is not necessary in allcases. This will become clear later. In order to detect a respectiveworkpiece edge, the height measuring device is for example provided withcontrast filters, median filters or other such filters in order todetect the course of an edge. For example, an evaluation device of theheight measuring device is provided with a logic which can detect astraight line, that is to say a workpiece edge. Moreover, the evaluationdevice is preferably configured such that it only recognises linesrunning transversely to the working direction as workpiece edges.

The height measuring device is advantageously configured to determinethe height of the workpiece in a direction or axis oriented orthogonallyto an upper side of the workpiece or workpiece upper side surface and/orto an underside of the workpiece or workpiece underside surface.

Preferably, the height measuring device is positioned such that themachine tool lies on the workpiece with the largest possible section ofthe guide surface or, in the case of a semi-stationary machine tool, alarge surface of the workpiece can lie on the guide surface if theheight measuring device carries out the measurement. For example,according to a preferred embodiment a section of the guide surfaceextends in front of the height measuring device, with which the guidesurface can be supported on the upper side of the workpiece or a guidedevice, for example a guide rail, lying on the upper side of theworkpiece. It is also possible that the workpiece can be supported onthis section of the guide surface, in particular in the case of asemi-stationary machine tool.

According to a preferred exemplary embodiment, the height measuringdevice is arranged on a for example rear longitudinal end region of theguide surface and a detection range, for example an optical axis, of theheight measuring device is oriented in the direction of the otherlongitudinal end region of the guide surface. For example, the heightmeasuring device can be arranged above the guide surface with itsdetection range directed obliquely downwards, in the direction of theguide surface.

The height measuring device preferably comprises at least onecontactless detecting or measuring sensor or exclusively contactlessdetecting or measuring sensors.

In the case of the height measuring device, different measuringprinciples are possible, for example capacitive, inductive or othermeasuring principles.

However, an optical system is preferred. The height measuring deviceexpediently comprises at least one optical sensor and/or a camera. Theoptical sensor could for example comprise a brightness sensor or severalbrightness sensors. A brightness sensor can for example be used todetect when a workpiece edge is passed over. If for example a referencemarking is to be identified, it can be identified by means of theoptical sensor, for example the brightness sensor, if the machine toolpasses over the respective workpiece edge.

It is also expedient if the height measuring device is provided with atleast one distance sensor. A distance between a sensor for detecting aworkpiece edge and the workpiece can for example be determined by meansof the distance sensor.

The height measuring device expediently comprises at least one referencelight source for generating a reference marking on the workpiece. Thereference marking is expediently particularly narrow or point-formed, inparticular linear or point-formed. The reference marking can for examplebe detected by an optical sensor or a camera of the height measuringdevice in order in this way to detect a workpiece edge of the workpieceby means of a light reflection of the reference light generated by thereference light source. Thus, if for example the reference light isinitially pointed past the workpiece and the workpiece and the machinetool are then moved relative to one another so that, during the courseof this movement, the light from the reference light source strikes theworkpiece, then this is first the case in the region of the lowerworkpiece edge. The height measuring device can detect the lowerworkpiece edge on the basis of the “first” reflection of the referencemarking on the workpiece, namely in the region of the lower workpieceedge.

According to a preferred concept, the height measuring device isconfigured to determine the height of the workpiece on the basis of achange in direction and/or change in speed of a light reflection of thereference light generated by the reference light source in the event ofa dynamic movement of the machine tool in relation to the workpiece, forexample transversely to a workpiece edge of the workpiece. Thus, if themachine tool is moved relative to the workpiece, so that the side of theworkpiece the height of which is to be measured is within the detectionrange of the height measuring device, for example in the region of theoptical sensor or the camera, the reference light illuminates the sideof the workpiece. The machine tool is for example moved forwards overthe workpiece along a first direction, in particular a typical workingdirection. The light reflection of the reference light thereby runs forexample from a lower workpiece edge to an upper workpiece edge of theworkpiece and thereby has a second direction relative to the sensor ofthe machine tool which is oriented at an angle to the first direction,for example an oblique movement direction. If the light beam from thereference light source moves over the upper workpiece edge, it is so tospeak continuously reflected from the workpiece surface so that thelight reflection is so to speak fixed in relation to the sensor withreference to the moved system, namely the moved machine tool, i.e. it nolonger exhibits any change in direction and/or relative movement. Theheight measuring device can then determine the height of the workpieceon the basis of this information.

Preferably, the height measuring device is configured to determine theheight of the workpiece on the basis of a distance travelled by thelight reflection transversely to a direction along which the machinetool is moved relative to the workpiece. For example, the heightmeasuring device can determine the height of the workpiece on the basisof the length of the movement in the second direction as well as,advantageously, additional information, for example a table and/or anassignment function. The length of the movement of the second directionis for example stored in a sequence of images, an individual image orthe like, of the height measuring device. It is possible that the heightmeasuring device evaluates the individual images directly, withoutstoring or buffering them, in order to determine the length of themovement in the second direction, for example as a so-called livestream. However, it is for example also possible that the machine tooldetermines the height of the workpiece on the basis of a relationbetween the movement in the first direction and the movement of thelight reflection in the second direction.

It is preferred if the reference light source or the optical sensor orboth are provided with an optical filter, for example a UV filter, acolour filter, a polarisation filter or the like. The optical filtersare preferably matched to one another such that the optical sensor isfor example optimally matched to the light colour and/or lightbrightness and/or polarisation of a reflection of the reference lightfrom the reference light source. For example, extraneous light whichdoes not originate from the reference light source is so to speakfiltered out through an arrangement of two polarisation filters on thereference light source and on an optical sensor, in particular thecamera, which are matched to one another. For example, interferingreflections caused by sunlight or other extraneous light can beeliminated in this way.

It is preferred if the height measuring device does not need a separatesensor and a sensor which is in any case mounted on the machine tool,for example a tool sensor, is used for the height measurement. Thesensor or an individual sensor of the height measuring device isexpediently formed by a tool sensor, for example a camera, an opticalsensor, a capacitive sensor or the like, for detecting a workpiececontact region in which the work tool is in contact with the workpieceand/or for detecting a section of the workpiece located in front of thework tool, viewed in a working direction. Thus, the sensor can forexample cover the region in which a saw blade or other work tool cutsinto the workpiece. However, a coverage of the front section of theworkpiece, viewed in the working direction, is also expedient. Forexample, a camera is directed forwards in the direction of the workpiecewhich is to be machined and at the same time serves as a component, orthe sole component, of the height measuring device.

It is further advantageous if the height measuring device is configuredto detect a machined edge formed through a machining of the workpiece bythe work tool. The height measuring device can thus at the same timealso detect a machined edge, for example a cut edge. Optical methodswhich are already advantageous in detecting a workpiece edge of theworkpiece can, so to speak, continue to be used for this purpose. Forexample, a contrast filtering, an edge detection or the like which is inany case provided on board the height measuring device can be used todetect a machined edge.

The machine tool is expediently provided with a display device, forexample a display, graphic display or the like, in particular a screen,for displaying information supplied by the height measuring device.Naturally, a simple display device, for example one or more LEDs or thelike can also be provided in order to compare or display the height ofthe workpiece. It is also possible that the height of the workpiece isfor example signalled in a manner simple for the operator to recogniseusing an LCD display or a segment display.

The information supplied by the height measuring device, which can bedisplayed on the display device, expediently comprises at least onemarking indicating or representing a workpiece edge. The information canalso, in particular in addition to the marking, display at least apartial region of the workpiece, for example its end face. In this way,the operator can for example recognise whether the marking which issupposed to indicate the workpiece edge is in fact an upper workpieceedge by comparing the marking with the synoptically displayed image ofthe workpiece. However, the information can also comprise a heightspecification for a height of the workpiece, for example a scale,numerical specification or the like. The marking is expedientlygenerated by the height measuring device on the basis of a detection ofthe upper workpiece edge and/or the lower workpiece edge. The operatorthus recognises, on the basis of the marking, whether the heightmeasuring device has correctly detected the upper workpiece edge orlower workpiece edge and output these accordingly as a marking on thedisplay device.

It is preferred if the machine tool is configured to determine aspecified penetration depth of the work tool on the basis of the heightof the workpiece determined by the height measuring device. That is tosay the machine tool so to speak specifies an optimal penetration depth.The operator can adhere to this recommendation in that for example theyonly move the work tool into the workpiece as far as the specifiedpenetration depth.

A servomotor-driven or semi-automatic concept is particularlyconvenient. An actuating drive is advantageously provided in order toadjust the drive unit relative to the guide element depending on thespecified penetration depth. The machine tool is configured to controlthe actuating drive according to the specified penetration depth, sothat the drive unit and thus the tool holder with the work tool aremoved to the ideal specified penetration depth.

However, a semi-manual or manual depth setting is also possible.Preferably, the machine tool is provided with a depth adjustment devicein order to set a penetration depth of the work tool in the workpiecewith at least one stop element which is adjustable according to thespecified penetration depth. The operator can fix the stop element onfor example a mounting contour of the depth adjustment device accordingto the specified penetration depth. Here too, a servomotor-drivenconcept is possible, i.e. the stop element is for example moved by anactuating drive into a position in relation to a mounting contour of thedepth adjustment device corresponding to the specified penetrationdepth.

A protected arrangement of the height measuring device is advantageous.The height measuring device is expediently arranged in a dust extractionregion and/or beneath a covering.

So to speak mechanical markings can for example be provided in order toorient the machine tool for a height measurement of the workpiece. Forexample, according to one variant the height measuring device uses amarking arranged on the guide element or on a housing, in particular adrive unit, of the machine tool in order to orient the machine tool to aworkpiece edge, for example the upper workpiece edge, of the workpiece.The marking is for example a linear marking, a projection, a depressionor the like. It is particularly advantageous if such a marking isprovided on a narrow side of the guide element. Furthermore, LEDs forexample or other such light sources can be provided in the region of themarking, so that the operator is displayed a reference position in orderto orient the machine tool in relation to the workpiece.

However, a marking superimposed on the display device is also suitablein order to orient the machine tool in relation to the workpiece. Forexample, according to one exemplary embodiment the height measuringdevice is configured to display an optical marking, for example a line,at least one individual point or the like, as well as a so to speaksynoptical image of the workpiece edge on a display device. In this way,the operator can also align the optical marking with the displayedworkpiece edge, so that as a result the machine tool is oriented inrelation to the workpiece for the height measurement.

According to a preferred concept, the height measuring device isconfigured to dynamically detect at least one workpiece edge, forexample an upper workpiece edge or a lower workpiece edge, of theworkpiece during a relative movement of the workpiece and the machinetool. It is thereby preferable if the machine tool is guided along onthe workpiece or the workpiece is guided along on the machine tool inthat the workpiece rests on the guide surface. In particular, the upperside of the workpiece or the underside of the workpiece lies against theguide surface. The height measuring device can for example dynamicallydetect if the workpiece edge is in a reference position.

It is possible that the height measuring device dynamically detects bothworkpiece edges and, in addition, also advantageously determines arelative distance of the detecting sensor from the end face of theworkpiece, so that the height measuring device determines the height ofthe workpiece on the basis of the relative distance and of a distancebetween the detected workpiece edges or of a distance between images ofthe workpiece edges.

The at least one tool sensor and/or the at least one position sensor isexpediently a contactless sensor or comprises such a sensor.

The mobile machine tool according to the invention can for example beguided relative to the workpiece as a manually-operated machine tool. Inparticular, the machine tool is so light that it can be grasped by anoperator and guided along on the workpiece. Such a machine tool is forexample a separating machine, a saw, a milling machine, in particular arouter, a plunge saw, a mitre saw, which for example has a guide railfor laying on the workpiece, a jigsaw or the like. It is also possiblethat the mobile machine tool is a so-called semi-stationary machinetool, i.e. a machine tool which can be transported conveniently to thelocation of use, for example on a construction site. In this case themachine tool is for example a mitre saw, a sliding saw, a sliding mitresaw, a bench saw or the like.

The work tool is preferably a cutting tool, for example a saw blade, acutting disc or the like. The work tool can be an elongated saw blade,for example for an oscillating saw, in particular a jigsaw, or acircular saw blade. Furthermore, the work tool can also be a millingtool, drilling tool or the like.

Exemplary embodiments of the invention are explained in the followingwith reference to the drawing, wherein:

FIG. 1 shows an oblique perspective view of a machine tool, viewedobliquely from the rear, which is shown in

FIG. 2 in an oblique frontal perspective view,

FIG. 3 shows a view of the machine tool according to FIGS. 1, 2, viewedobliquely from above,

FIG. 4 shows the machine tool according to the preceding figures viewedfrom the side and from obliquely below, wherein a cover has beenremoved,

FIG. 5 shows a detail of an illumination device of the machine toolaccording to the preceding figures,

FIG. 6 shows a side view of the machine tool according to the precedingfigures in a central adjustment position,

FIG. 7 shows the view according to FIG. 6, wherein however the machinetool occupies a lower adjustment position,

FIG. 8 shows a perspective view of the machine tool according to thepreceding figures as well as a guide rail for same,

FIG. 9 shows the machine tool in an upper adjustment position inrelation to its guide element, in schematic representation,

FIG. 10 shows the view according to FIG. 9, but with the drive unitroughly in the adjustment position according to FIG. 6,

FIG. 11 shows a view of the machine tool according to FIGS. 9, 10,wherein the drive unit occupies an adjustment position roughly as shownin FIG. 7,

FIGS. 12-14 show a display device of the machine tool according to thepreceding figures in the adjustment positions shown in the FIGS. 9-11,

FIGS. 15-17 in each case show a workpiece being machined by the machinetool in the adjustment positions according to FIGS. 9-11 and the cuttingline thereby formed,

FIG. 18 shows a schematic representation of a detection range of a toolsensor of the machine tool during detection of a front cut edge ormachined edge, viewed in the working direction

FIG. 19 shows progressions of pixels relative to a position signal of aposition sensor of the machine tool in connection with therepresentation according to FIG. 18,

FIG. 20 shows a progression of optically displayed cut edges on thedisplay device of the machine tool in connection with the representationaccording to FIG. 18,

FIG. 21 shows a schematic representation explaining a detection of theguide rail shown in FIG. 8,

FIG. 22 shows a schematic circuit diagram of the machine tool with aprocessor,

FIG. 23 shows a flow chart representing the generation of for examplethe information according to FIGS. 19, 20,

FIG. 24 shows the sequence of an image processing in the case of amachined edge detection according to FIG. 18,

FIG. 25 shows a flow chart in connection with the specification of atarget position of the drive unit of the machine tool relative to itsguide element,

FIG. 26 shows a flow chart representing the output of an actual relativeposition of the drive unit relative to the guide element,

FIG. 27 shows a detection range of a tool sensor of the machine toolwith reference markings,

FIG. 28 shows an arrangement of reference markings for an intrinsiccalibration of the tool sensor of the machine tool,

FIG. 29 shows an alternative exemplary embodiment of a machine toolaccording to the invention in the form of a semi-stationary machinetool,

FIG. 30 shows a schematic view of the machine tool according to FIGS.9-11 with a height measuring device,

FIG. 31 shows a display device of the machine tool according to FIG. 30with image information supplied by the height measuring device,

FIG. 32 shows a highly schematic representation of the machine toolaccording to FIG. 30 and the height measuring device in connection withthe measurement of a first workpiece,

FIG. 33 shows the arrangement according to FIG. 32, but during themeasurement of another, thinner workpiece,

FIG. 34 shows a diagram of a progression of a number of pixels inrelation to a workpiece height, wherein the number of pixels can bedisplayed on the display device according to FIG. 31,

FIG. 35 shows a schematic representation of a detection range of a toolsensor of the machine tool during detection of a rear cut edge ormachined edge, viewed in the working direction,

FIG. 36 shows progressions of pixels relative to a position signal of aposition sensor of the machine tool, in particular in connection withthe representation according to FIG. 35,

FIG. 37 shows a progression of optically displayed cut edges on thedisplay device of the machine tool,

FIG. 38 shows a schematic detail view illustrating a height measuring ofa workpiece.

A machine tool 10 is for example configured as a sawing machine. Inparticular, the machine tool 10 is a plunge saw.

The machine tool 10 has a drive unit 11 with a machine housing 12 inwhich a drive motor 13 is housed. The drive motor 13 drives a toolholder 14 directly or via gears, not shown in the drawing. In thedrawing, a work tool 15 is fastened, or in any case detachablyfastenable, onto the tool holder 14. The work tool 15 comprises forexample a saw blade or other cutting tool. It should be mentioned atthis point that the exemplary embodiment also stands for other machinetools of mobile type, i.e. for example hand-guided cutting machines,routers or the like.

The machine tool 10 is mobile, i.e. it can be supplied with power via apower supply connection 17. The drive motor 13 is an electrical drivemotor, wherein, alternatively, a pneumatic or other drive motor isreadily conceivable. The power supply connection 17 comprises forexample a mains cable 17B, on which a plug 18B for plugging into a mainssupply, for example a 110V or 230V alternating current supply, a directcurrent supply or the like is arranged. However, in this specificembodiment the mains cable 17B is to be understood as an option, i.e.the machine tool 10 can be cordless or operable without a mains cable,i.e. the power supply connection 17 comprises for example plug contacts,which cannot be seen in the drawing, which allow an energy store 18, inparticular a so-called rechargeable battery pack, to be connecteddetachably. The energy store 18 supplies the machine tool 10 withelectrical energy. This makes the machine tool 10 optimally mobile.

A handgrip arrangement for gripping the machine tool 10 is arranged onthe drive unit 11. This facilitates the handling of the machine tool 10.The handgrip arrangement comprises for example an upper handgrip 19 aswell as a front handgrip 20, viewed in a working direction AR. Theoperator can thus grasp the handgrips 19, 20 and so guide the machinetool 10 along a workpiece W in the working direction AR, as well asadjusting it if necessary into an inclined position in relation to aguide element 30.

The work tool 15 is at least partially housed beneath a protective coveror enclosure device 21. In particular if the drive unit 11 assumes anupper adjustment position SO or basic position in relation to the guideelement 30, the work tool 15 is substantially completely accommodatedbeneath the enclosure device 21.

The enclosure device 21 also forms a boundary of a dust extraction duct22, which so to speak extends around the upper section of the work tool15 or the section of the work tool 15 which is enclosed within theenclosure device 21. The dust extraction duct 22 ends in an extractionconnection 23, to which for example a suction device 100 or otherextraction device can be connected. For example, a suction hose 101 canbe connected to the extraction connection 23 which connects theextraction connection 23 with the suction device 100 with respect to aflow, i.e. it establishes a flow connection.

The dust extraction duct 22 and/or the enclosure device 21 are coveredby a cover 24. The cover 24 is removable, as can be seen for example inFIGS. 3 and 4.

A display device 25, by means of which the functions of the machine tool10 can be monitored and/or controlled, is located on an upper side ofthe machine tool 10 or the drive unit 11 facing the operator. Forexample, the display device 25 comprises a display 26, in particular ascreen. The display 26 can be monochrome, but also multicoloured. Inparticular, the display 26 contains numerous graphically controllablepicture elements or pixels. The picture elements or pixels are forexample arranged next to one another in an X-direction and above oneanother in a Y-direction and are in particular individuallycontrollable.

By means of an electrical drive switch 27, the operating element ofwhich is visible in the drawing, the drive motor 13 can be switched onand off and also, in particular, adjusted with respect to its rotationalspeed. The operating element or the drive switch 27 are located on anupper section of the handgrip 19 facing the operator, so that if theygrasp the handgrip 19 the operator can for example operate the operatingelement 27 with their index finger.

As is also ergonomically favourable, an operating element 28 for a depthadjustment device 40 is located near the handgrip 19. The operatingelement 28 can be used to unlock the depth adjustment device 40, so thatthe drive unit 11 can be moved out of the adjustment position S0 intoadjustment positions S1 and S2, which are illustrated by way of example.

The guide element 30 forms for example a saw bench. The guide element 30is plate-like. For example the guide element 30 comprises a guide plate31. A guide surface 32 is provided on the underside of the guide element30 facing away from the drive unit 11 with which the machine tool 10 canbe guided along an a underlying surface, for example the workpiece W ora guide rail 50. The guide surface 32 is preferably a flat surface.

Depressions and/or a guide groove 33 into which a guide projection 52 ofthe guide rail 50 can engage can be provided on the guide surface 32.Naturally, the kinematic reverse is possible, i.e. that a guideprojection is provided on the guide element 30 in order to engage in adepression of the guide rail 50 (not illustrated).

The drive unit 11 can be adjusted in relation to the guide element 30 bymeans of a bearing arrangement 35, which is in the present caseswivelable. However, a sliding displacement would also readily bepossible in order to adjust different depth adjustment positions oradjustment positions S0-S2. This should for example be realised in thisway in the case of a router with corresponding guide columns.

The bearing arrangement 35 comprises in particular a depth adjustmentbearing 36. The depth adjustment bearing 36 is located at the rear,viewed in the working direction AR, whereby a depth adjustment bearinglocated at the front, viewed in the working direction, is also readilypossible in the case of an embodiment of the machine tool 10 as apendulum hood saw or as a combined pendulum hood-plunge saw. Theadjustment positions S0-S2 as well as adjustment positions between thesecan be adjusted by means of the depth adjustment bearing 36.

Furthermore, a mitre position or swivel position of the drive unit 11 inrelation to the guide element 10 can be adjusted, for which purpose atilt bearing 37 is provided. The tilt bearing 37 comprises bearingelements 38 which, viewed in the working direction AR, are arranged atthe front and rear on the drive unit 11 as well as on the guide element30. The drive unit 11 is arranged between the bearing elements 38.

The drive unit 11 can be swivelled around a depth adjustment axis TS bymeans of the depth adjustment bearing 36. The drive unit 11 can beadjusted in relation to a tilt axis SA in relation to the guide element30 by means of the tilt bearing 37, in particular the mitre bearing. Thetilt axis SA runs parallel to the working direction AR, the depthadjustment axis SA runs transversely, in particular at right angles toworking direction AR.

The operator can specify a desired depth adjustment on the machine tool10 by means of a depth adjustment device 40. The depth adjustment device40 comprises a mounting contour 41, for example on an upper side orfront side of the enclosure device 21, configured as a guide. The guideor mounting contour 41 further comprises a scale 42 on which theoperator can read a respective depth adjustment position or adjustmentposition S0-S2 as well as intermediate positions.

A stop element 43 is mounted moveably on the guide or mounting contour41, which the operator can fix in the desired depth adjustment positionor adjustment position S0-S2. For example, a snap-locking device orclamping device is provided on the stop element 43, that is to say afixing device 44 by means of which the stop element 43 can be fixed indifferent depth adjustment positions on the guide or mounting contour41. For example, an operating element 45 is provided on the stop element43 by means of which the fixing device 44 can be switched from asnap-locking position and/or clamping position into a release positionin which the stop element 43 is adjustable in relation to the guide ormounting contour 41. In a respective depth adjustment position of thestop element 43, a stop 29 on the drive unit 11 comes to rest againstthe stop element 43, so that the respective adjustment position S0-S2 ordepth adjustment position can be adjusted in this way.

The guide rail 50 forms a guide device 50A for guiding the machine tool10 along a working direction AR.

The guide rail 50 has an upper side 51 along which the guide element 30can slide. The guide projection 52 projects in front of the upper side51, for example in the manner of a guide rib. The guide rail 50 has anelongated form, so that the machine tool 10 can be guided along thelongitudinal extension of the guide rail 50 and thus in the workingdirection AR. This makes possible, in a known manner, particularly exactand straight saw cuts in the workpiece W.

An underside 53 of the guide rail 50 is intended to rest on theworkpiece W or other underlying surface. A narrow side 54 of the guiderail 50 past which the work tool 15 can be moved in the direction of theworkpiece W extends laterally, i.e. transversely to the longitudinalextension of the guide rail 50. An upper edge 55 extends between theupper side 51 and the narrow side 54. The operator can thus move themachine tool 10 positioned on the guide rail 50 comfortably from thelongitudinal end 56 of the guide rail 50 up to its longitudinal end 57.

The machine tool 10 is provided with a sensor arrangement 60 whichcomprises a plurality of sensors. For example, tool sensors 61, 62 inthe form of cameras are provided. The tool sensor 61 is arranged at thefront, viewed in the working direction AR, the tool sensor 62 isarranged at the rear, viewed in the working direction AR, in relation tothe work tool 15. The tool sensors 61, 62 serve to cover partialworkpiece contact regions WK1, WK2, in which the work tool 15 is incontact with the workpiece W, for example cutting into the workpiece W.

Both tool sensors 61, 62 are so to speak arranged in the dust chamber ordirt chamber of the machine tool 10, namely in the region of theenclosure device 21. This has the advantage that, apart from the typicaldust intake or other soiling, the tool sensors 61, 62 are not exposed toenvironmental influences. In particular, the tool sensors 61, 62 can bearranged optimally in relation to their respective image recognition,which will be explained later.

The dust extraction via the extraction connection 23 in itself alreadyensures that the detection ranges or measurement regions of the toolsensors 61, 62 are blown largely free of particles P which are producedduring the machining of the workpiece W by the work tool 15.Nonetheless, even in the case of an optimal particle extraction or dustextraction, particles P, in particular chips, dust or the like, arepresent in the detection ranges of the tool sensors 61, 62 which canadversely affect or even prevent the capture of an image. In order tocounter this problem, optimisation means OPT are provided which areintended to reduce, or preferably eliminate, the effects of theparticles P present in the detection ranges of the tool sensors 61, 62on a tool sensor signal from these tool sensors 61, 62.

The optimisation means OPT comprise for example a suitable angulararrangement of optical axes of the tool sensors 61, 62 in relation to anillumination of the detection ranges of the tool sensors 61, 62.

An optical axis O1 of the tool sensor 61 runs for example at an angle ofapprox. 60-90° in relation to the guide surface 32. The tool sensor 61is configured and/or intended to cover the work tool 15 in particular ina roughly tangential manner. A direction of view or an orientation ofthe detection range of the tool sensor 61 is for example indicated inFIG. 18.

An optical axis O2 of the rear tool sensor 62, viewed in the workingdirection AR, is likewise oriented at a steep angle in relation to theguide plane 32 and thus also roughly tangentially in relation to thework tool 15. The tool sensor 62 serves to detect a rear cut edge whichis created when the work tool 15 cuts into a workpiece W.

The tool sensors 61, 62 are located so to speak in a dark space. Theyare substantially covered by the enclosure device 21. The detectionranges of the tool sensors 61, 62 are thus located in a space protectedagainst the influences of extraneous light, in particular if the guidesurface 32 rests on the workpiece W.

However, the tool sensors 61, 62 do not need to be highly sensitive orsuitable for low-light environments, but can achieve an optimaldetection performance. To this end, an illumination device 70 isprovided which comprises several light sources 71, 72 as well as anarrangement of several light sources 73 in a row, i.e. a light sourcearrangement 73.

In order to adapt the brightness of the illumination device 70, forexample to a brightness of the environment of the machine tool 10, theillumination device 70 can for example be provided with a brightnesssensor 69 with which a brightness of an environment of the machine tool10 can be registered.

The light source 71 and the light source arrangement 73 are assigned tothe tool sensor 61. The light source 71 and the light source arrangement73 in each case illuminate the work tool 15 from opposite sides in theregion of a workpiece contact region, namely of a region in which thework tool 15 cuts into the workpiece W.

The light source 72 is assigned to the tool sensor 62 and illuminatesthe detection range of same.

In principle, reflections and mirroring or the like could occur when theillumination device 70 is switched on. However, in order to reduce ifnot actually prevent a negative influence of the illumination device 70on the image quality or detection quality of the tool sensors 61, 62,the optical axes O1 and O2 of the tool sensors 61, 62 are oriented atwide angles in relation to the main light axes or light beam axes of thelight sources 71-73.

For example, the light beam axis or main axis L1 of the light source 71is oriented at an angle W12 to the optical axis O1 of the tool sensor 61in a plane parallel to the guide surface 32 and at an angle W11 in aplane vertical to the guide plane or guide surface 32. The angles W11and W12 are angles of more than 90°, so that for example the lightemitted by the light source 71 strikes particles P which are producedduring the machining of the workpiece W by the work tool 15 at an angleto the optical axis O1. As a result, the particles P are not illuminatedin the optical axis O1 of the tool sensor, in particular the camera 61,so that they appear less bright in the image captured by the tool sensor61 or do not interfere with the image.

The light beam axis or main axis of the light sources 73A, 73C of thelight source arrangement 73 is also oriented at an angle to the opticalaxis O1, for example roughly at right angles, corresponding to an angleW3 (FIG. 3).

A similar angled orientation, at least in relation to a plane parallelto the guide surface or guide plane 32, is also provided in relation tothe tool sensor 62 and the light source 72, for example at an angle W2between the optical axis O2 and the light beam axis or main axis L2 ofthe light source 72. The angle W2 amounts for example to at least 30 or40°.

According to a further measure improving the image quality, the lightfrom the illumination device 60 is as far as possible emitted in adiffuse and non-directed manner. For example, the light sources 71 andthe light source arrangement 73 are in each case arranged behinddiffusing elements 74, 74. This is naturally also advantageous in thecase of the light source 72. The diffusing elements 74, 75 comprise forexample diffuse lenses, matte lenses or the like.

It is also advantageous for the detection of for example a frontmachined edge or a front edge of the work tool 15, as can be seen inFIG. 5 in particular, that the illumination takes place from oppositesides of the work tool 15. In this way, unfavourable hard shadows areavoided. Thus, one can see from FIGS. 3-5 an optimal illuminationconcept which significantly improves the image quality of the imagesignals generated by the tool sensors 61, 62.

Further advantageously, the sensor arrangement 60 is provided withfurther sensors, for example a position sensor 63 which is assigned tothe depth adjustment device 40. The position sensor 63 can for exampledetect a respective position of the stop element 73 in relation to theguide or mounting contour 41.

A further position sensor 64 is for example arranged on the depthadjustment bearing 36, so that it can register the respective angularposition of the drive unit 11 in relation to the guide element 30.

The sensor arrangement 60 expediently also comprises a tilt sensor 65which can specifically register an angular position or tilt of the driveunit 11 relative to the guide element 30. The tilt sensor 65 could alsobe formed by a correspondingly adjusted or selected acceleration sensor66 which registers an acceleration of the drive unit 11 or the machinetool 10. The acceleration sensor 66 can for example register anacceleration of the drive unit 11 in the direction of the guide surface32 if the drive unit 11 swivels around the depth adjustment axis TS.Furthermore, the acceleration sensor 66 can register an accelerationparallel to the guide plane or guide surface 32, so that an advance ofthe machine tool 10 relative to the underlying surface or workpiece Wcan be detected by means of the acceleration sensor 66.

Furthermore, the machine tool 10 can also be provided with other toolsensors, in particular tool sensors which are arranged next to oneanother in a row direction or row arrangement. By way of example,further tool sensors 161, 162, in particular optical sensors,advantageously cameras, are provided on the cover 24 or on the oppositeside of the drive unit 11 from the cover 24. A saw cut SN which themachine tool 10 cuts into the workpiece W can be monitored even moreprecisely by means of the tool sensors 161, 162.

However, tool sensors can also be provided outside of the dustextraction chamber, i.e. outside of the enclosure device 21, for exampletool sensors 261, 262, which are in particular arranged directly next tothe bearing elements 38 on the guide element 30. The detection ranges ofthe tool sensors 261, 262, which are advantageously formed by camerasbut which can also realise other sensory concepts, are for exampledirected frontally onto the work tool 15 from the front and from therear.

It is advantageous if a tool sensor oriented in the working direction ARis provided which is so to speak oriented forwards in the direction ofview towards the workpiece. For example, a detection range EB3 of a toolsensor 263 (FIG. 1) is oriented forwards, viewed in the workingdirection AR. The tool sensors 261, 263 can be arranged on the samemounting element, one tool sensor 261 being oriented rearwards, viewedin the working direction AR, towards the work tool 10, the other toolsensor 263 being oriented forwards, viewed in the working direction AR.

An optimal concept for reconciling a machined edge or several machinededges actually created in the workpiece W by the work tool 15 and theposition signal POS of the position sensor 63 is explained in thefollowing with reference to FIGS. 9-17. The position sensor 63 comprisesfor example a resistance measuring strip which is arranged on the guide61 and influenced by the stop element 43. However, alternatively or inaddition, an optical detection, a distance measurement or the like ofthe stop element 43 relative to the guide surface 32 is possible.

Starting out from the adjustment position S0 (FIG. 9), the drive unit 11is adjusted, via one or more intermediate positions S1, into the loweradjustment position S2 (FIG. 11) in which the work tool 15 cuts to amaximum extent into the surface of the workpiece W and/or projects infront of the guide surface 32. In the adjustment position S0 the stop 43is for example still in the uppermost position (FIG. 9). As yet, no sawcut has been displayed on the display device 25. Nonetheless, the toolsensor 61, 62 can also already represent certain working regions, whichfor reasons of simplification is not illustrated in the drawing. Theworkpiece W is also still unmachined, i.e. according to FIG. 15 it has auniform “undamaged” surface.

If the drive unit 11 is swivelled around the depth adjustment axis TS,the stop 29 carries with it the stop element 43, as long as it is notyet fixed on the guide or mounting contour 41, until it reaches thelower position illustrated in FIG. 11. At the same time the positionsignal POS output by the position sensor 63 changes.

In the adjustment position S1 (FIGS. 10, 13, 16), a saw cut SN which iscut into the workpiece W by the work tool 15 extends between a frontmachined edge KV1 and a rear machined edge KH1. The saw cut SN hat a cutlength SL1. The position sensor 64 outputs an actual position signalIST1 and IST2 for the two machined edges corresponding to the front andrear cut edges KV1, KH1. However, in an illustrated lower position ofthe stop element 43 as shown in FIG. 11, the drive unit 11 can assumethe target adjustment position S2 (if the stop element 43 is adjusted toits lowest position/FIG. 11), which is indicated on the display device25 by target markings SO1 and SO2 for the front and rear cut edges KVand KH.

During the further adjusting movement around the swivel axis TS, theactual markings IST1 and IST2 converge until they coincide with thetarget markings SO1 and SO2. The saw cut SN then has a cut length SL2and extends from its front cut edge KV2 to its rear cut edge KH2.

The illustration according to FIGS. 9-17 is thus based on an optimallyadjusted configuration which however needs to be “calibrated”beforehand. This is made more clear in the following with reference toFIGS. 18-20:

FIG. 18 shows schematically a detection range EB1 of the tool sensor 61.Within the detection range 61, an evaluation device 80 of the machinetool 10 identifies for example a test region PB within which the frontmachined edge KV is to be determined. The front machined edge KV or cutedge is cut by the work tool 15, which is indicated schematically. Itshould be mentioned at this point that during operation, i.e. if it isdriven by the drive motor 13, the work tool 15 in any case appears outof focus, for which reason the broken line 15 also represents therelatively not clearly recognisable work tool 15. In any case the frontmachined edge KV is formed, which is only identified by the evaluationdevice 80 within the test region PB. In the image according to FIG. 18the machined edge KV lies slightly in front of the outer circumferenceof the work tool 15, which appears out of focus in the image. The imageaccording to FIG. 18 is very close to reality, because one can see thatthat the front machined edge KV is only very small or narrow within thedetection range EB1 or test region PB. The greater part of the machinededge KV is covered by the work tool 15, i.e. it cannot be detected bythe tool sensor 61.

Preferably, the test region PB is substantially limited to the region ofthe front machined edge KV.

It will be made clearer in the following with reference to FIG. 19 howan adjusted depth adjustment position of the drive unit 11 relative tothe guide element 30 is so to speak calibrated or assigned on the basisof the position signal POS of the position sensor 63. The positions ofdisplay pixels on the display device 25 are entered on an axis SP, theposition signal POS of the position sensor 63 on an axis POS. If thestop element 43 of the stop 29 is carried along during a plungingmovement or adjusting movement of the drive unit 11 relative to theguide element 30, i.e. moved in the direction of the guide surface 32(see FIGS. 9-11), the position signal POS increases so to speak. At thesame time the pixels of the machined edge KV are determined as positionvalues PX and PY.

To illustrate this more clearly, the result is significantly exaggeratedin FIG. 20. For example, the cut edge or machined edge KV0 runsrelatively obliquely just as the work tool 15 cuts into in the workpieceW. For example, an ideal path or an ideal orientation of the machinededge KV0 would be substantially horizontal or in the X-direction if thetool sensor 61 is optimally oriented and the movements run more or lessparallel. The machined edge KV0 moves in the Y-direction during thecreation of the saw cut. In the adjustment position S1, the machinededge KV1 is formed which already runs significantly more horizontallythan the machined edge KV0 or its image on the display device 25.

An analogous procedure is also readily possible on the basis of thesignal of the position sensor 64 in order to detect the swivel positionor adjustment position of the drive unit 11 relative to the guideelement 10.

In FIGS. 35-37, the situation in the region of the rear machined edge KHis illustrated in a manner comparable with the representation accordingto FIGS. 18-20 showing the front machined edge KV. It can be seen thatthe rear machined edge KH so to speak wanders downwards to the rearwithin the test region, likewise referred to, for the sake ofsimplicity, as the test region PB, (FIG. 35). Accordingly, developmentsof the machined edge KH, starting out from a machined edge KH0immediately following cutting into the workpiece W up to the machinededge KH1 in the adjustment position S1, are represented on the displaydevice 25.

The evaluation device 80 is also configured to determine whether themachine tool 10 is being operated with or without a guide rail 50 inthat the aforementioned calibration is expediently carried out once witha guide rail 50 and once without a guide rail 50, so that any toleranceswhich result from the position of the guide element 30 in relation tothe guide rail 50 and/or the guide rail 50 itself are determined, sothat an optimal display of a respective target position SO1 and SO2 ispossible with and without guide rail 50. If the calibration according toFIGS. 19 and 20 is carried out, the operator can adjust the stop element43 to a desired sawing depth or machining depth. The respective targetmarkings SO1 and SO2, which represent the machined edges which result ifthe drive unit 11 is adjusted as far as the stop element 43, appear onthe display device 25. The operator can then line up the target markingsSO1 and/or SO2 with a workpiece marking MA, for example on the surfaceof the workpiece W, so that the plunge cut or saw cut is exactly limitedor ends where the displayed marking SO1 and SO2 is displayed by thedisplay device 25. This makes possible a particularly exact and precisemachining of the workpiece.

It is thus advantageous if the guide rail 50 is detected by the toolsensor 61, 62 and/or the evaluation device 80.

Measuring fields M1-M4 are for example provided in order to ensurereliable detection of the guide rail 50, for example in the detectionrange EB1 of the front tool sensor 61, viewed in the working direction.In the measuring fields M1 and M2, the evaluation device 80 registersfor example an edge K3 between the guide element 30 and the guide rail50, in the detection range M2 it registers the edge of the guide rail 50in relation to the underlying surface, for example the narrow side 54 orthe upper edge 55. The edge K3 can for example be identified through acontrast measurement and/or by means of an in particular gradient-basededge filter. The contrast between the guide rail 50 and the workpiece Wis likewise used in order for example to identify the edge K5.Preferably, the edge K5 is determined with reference to the edge K3 orstarting out from the edge K3.

However, it would also be sufficient to identify one of the edges. Forexample, the presence of the guide rail can be identified by means ofanother measurement or sensory detection, in particular an opticaldetection of unique features of a guide rail, for example its structure,colour, longitudinal extension or the like.

In addition, in order to make the measurement so to speak particularlyreliable, a contrast measurement is also carried out with the measuringfields M3 and M4 in order to determine the contrast between guide rail50 and workpiece W, which serves as an indication that the machine tool10 is not resting on a workpiece W which has more or less the brightnessof a guide rail.

However, a measurement in individual measuring fields is not essential.For example, the intelligent evaluation device 80 can for exampledetermine that a long edge, for example the edge 55, is present, inorder in this way to conclude the presence of the guide rail 50. If, inaddition, a contrast measurement or a colour measurement or both is alsocarried out on both sides of the already identified guide rail edge K5,and these colours or contrasts are compared with one another (accordingto the measurement in the fields M4 and M3), this makes it possible todetect reliably that the machine tool 10 is actually standing on theguide rail 50 and not on a workpiece.

A method V1 for determining assignment values on the basis of theposition sensor signal POS, as well as the machined edge detectionaccording to FIG. 18, is presented with reference to FIG. 23.

The method begins starting out from an initial method step V11 in whichfor example a user selects a calibration. In the step V11 the userselects the calibration for example because a saw blade or work tooland/or the guide rail has been exchanged.

In a method step V12 it is for example first determined whether or notthe machine tool 10 is standing on the guide rail 50.

In a method step V13 the stop element 43 is coupled, for examplesnap-locked, clamped or the like, with the stop 29, so that a plungingmovement or adjusting movement of the drive unit 11 at the same timeresults in an adjustment of the stop element 43.

In an optional step V14, the position sensor 64 determines a currentangular position on the depth adjustment bearing 63.

In a method step V15, the position sensor 63 determines the respectiveposition of the stop element 43, i.e. the adjusted depth.

In a method step V16, the individual machined edges according to FIG. 18are displayed by the evaluation device 80. In a method step V17, therespective position sensor values POS as well as the values PX, PYdetermined through the cut edges or machined edges are stored. In thisway, the evaluation device 80 can for example store a correspondingassignment table 83 in a memory 82. However, alternatively or inaddition, the evaluation device 80 can also generate mathematicalassignment functions 83A, 83B from the values POS, PX and PY, forexample a third degree polynomial, fourth degree polynomial or the like.A number of position values PX, PY and POS thus suffice in order togenerate corresponding polynomials or other mathematical assignmentfunctions 83A, 83B. The accuracy of the mathematical assignmentfunctions 83A, 83B increases with an increasing number of availableposition values PX, PY and POS.

Preferably, an averaging and/or a weighting of the position values iscarried out in order to determine the assignment function 83A and/or83B. Preferably, the least squares method is used in order to determinethe assignment function 83A and/or 83B.

The step V18 represents the end of the method V1. However, the methodsteps V27 and/or V28 of the method V2 described in the following couldalso be realised in the step V18.

The evaluation device 80 can follow a similar procedure for the rearmachined edge KH and thereby for example generate mathematicalassignment functions 183A, 183B on the basis of position values PxH andPyH.

If the work tool 15 is removed from the workpiece W, the localisation ofthe test region PB can for example take place as follows. It shouldthereby be taken into consideration that for example the position of thesaw cut SN and thus for example its right-hand machining contour BK,viewed in the working direction AR, for example an elongated sawn edge,changes in relation to the tool sensor 61, 62, i.e. the camera,depending for example on the height of the guide rail 50, the width ofthe work tool or saw blade 15, the geometry of teeth or other cuttingcontours of the work tool 15 and the like. For example, the saw cut SNis first made in the workpiece W. The evaluation device 80 then detectsthe machined edge BK and, depending on the development and theorientation of the machined edge BK in the detection range EB1,determines a left-hand limit PLI, viewed in the working direction AR,and a right-hand limit PLR, viewed in the working direction AR, betweenwhich the machining contour BK of the test region PB is located.

The method V1 is preferably then carried out.

The image processing or edge detection according to FIG. 18 can forexample take place by means of the method V2 explained in the following.

In the method V2, the image captured by the tool sensor 61 is forexample, in a method step V21, first converted into a greyscale image,and in a method step V22 modified by means of a filtering orcompensation processing, for example a Gaussian filtering, medianfiltering, bilateral filtering, averaging filtering or the like.

In a method step V23, the test region PB is determined or masked.

In method step V24, a threshold method is applied, i.e. the greyscaleimage already generated in step V21 is for example converted into abinary image. For example, the workpiece surface thereby appears white,the cut edge or machined edge black.

The method steps V21, V22 and V24 comprise for example digital filters.

One or more of the method steps V21, V22 and V24 represent for example acomponent of the optimisation means OPT.

A method step V25 stands for an edge detection in the image generated instep V24.

In a method step V26, the values PX and PY are determined in that forexample the corresponding light and dark pixels in the image obtained inthe method step V25 are analysed.

In an optional method step V27, the curves PX and PY (FIG. 19) aredetermined, for example the aforementioned polynomials.

Not only in connection with the method V2, but quite generally inconnection with the invention, it is advantageous if confirmationqueries take place, namely such that only positions of cut edges whichare actually present are stored as pixel positions, so that for exampleoutside influences are ruled out. Such outside influences can forexample be dust, chips or other such blurring or foreign bodies.

Furthermore, when registering an edge in terms of the invention it isadvantageous if the plausibility of the edge is recognised or analysedfor example on the basis of neuronal networks or the like. A neuronalnetwork can for example be trained in advance for this purpose.

The assignment table 83 and/or the assignment functions 83A, 83B are forexample generated in a method step V28.

The sequence of the method steps V21 and/or V22 and/or V23 and/or V24can also be different. Also, in some cases individual method steps arenot necessary. For example, the test region PB, method step V23, can bedetermined first before the method steps V21, V22 are carried out.

The information obtained in the methods V1 and V2 can be used in themethods V3 and V4.

For example, in a step V31 of the method V3 the user can set acorresponding plunge depth by moving the stop element 53 into thedesired position. In a method step V32, the evaluation device 80determines whether or not a guide rail 50 is present.

In a method step V33, the position sensor 63 measures the positionadjusted by means of the stop element 43.

In a method step V34, the adjusted target position SO1, SO2 is displayedon the display device 25. At this point it becomes clear that the methodaccording to FIGS. 18, 19, 20 is carried out not only in connection withthe front tool sensor 61, but also with the rear tool sensor 62, so thata front and rear target machined edge is displayed to the operator onthe display device 25.

The method V4 stands for the display of an actual adjustment position ofthe drive unit 11 relative to the guide element 30. The adjustmentoperation of the drive unit 11 relative to the guide element 30 beginsin a method step V41. In a method step V41 the position sensor 64measures the respective swivel position or adjustment position of thedrive unit 11 relative to the guide element 10.

In a method step V43, the evaluation device 80 determines, for exampleon the basis of the assignment table 83 or the curves PX, PY accordingto FIG. 19, the actual position occupied by the drive unit 11 relativeto the guide element 10, or which machined edge results in the currentposition.

The method step V44 represents the end of the method V4. In this methodstep, the markings IST1 and/or IST2 are for example displayed.

The methods V1-V4 are carried out by the evaluation device 80. Themethods V1, V2, V3, V4 are for example realised by means of programmodules PV1, PV2, PV3, PV4 which contain program code which can beexecuted by the processor 81, wherein the methods V1-V4 are carried outon execution of the program code.

A certain imprecision can arise as a result of the installation of thetool sensors 61, 62, through an impact load on the machine tool 10, inparticular due to being dropped or the like, in that for example thetool sensor signals from the tool sensors 61, 62 generate anunfavourably oriented image for the display device 25. It has alreadybeen mentioned in connection with FIG. 20 that for example the machinededges should as such be displayed parallel to the Y-direction, but canbe oriented obliquely in the image. It is also important that forexample the test region PB can be detected reliably. It is for exampleadvantageous if the test region PB is oriented exactly or as exactly aspossible on the long cut edge created when the tool 15 plunges into theworkpiece surface, i.e. in the Y-direction, so that incorrectinformation can be avoided or reduced during calibration.

Advantageous measures are provided for this purpose:

For example, a reference marking R1 is provided in the region of theguide element 30 which can serve to orient the detection range or thedisplayed image area of the tool sensor 61 and/or 62.

It is firstly assumed that the cameras or tool sensors 61, 62 arealready intrinsically calibrated, so that optical errors, for examplewide-angle errors or the like, curvatures which result from the opticsof the tool sensors 61, 62 etc. are already “eliminated”. Thus, withreference to a reference marking R2 the tool sensor 61, 62 can so tospeak determine its position and/or orientation in space or theevaluation device 80 can determine the position of the tool sensor 61,62 within the installation space of the machine tool 10. This makespossible for example a so-called extreme calibration of the tool sensor61, 62.

It can be seen that the reference pattern R2 is for example acheckerboard pattern, the lines of which converge or diverge, or in anycase assume a particular angular position, depending on the perspective.This is the basic position for the determination of the spatialarrangement of the optical axis O1 or 02 of the respective tool sensor61, 62 by the evaluation device 80. Also suitable as reference patternis for example a so-called data matrix pattern, a radial geometricalpattern or the like. The evaluation device 80 simply needs to know theundistorted geometry (path of edges, length of edges and the like) ofthe respective reference pattern.

However, in simple cases an orientation on a straight line or on atwo-dimensional marking can also suffice, for example on a side edge ofthe guide plate 31 or on the reference marking R1.

A further reference marking R3 is for example represented by a side edgeor edge line (RM1) of the guide element 30 and/or an outer edge (RM2) ofthe work tool 15. It can be seen in FIG. 27 that the reference markingR3 lies inclined at angle within the detection range EB2, i.e. inclinedat angle in relation to an X-axis XE and a Y-axis YE of the detectionrange EB2. However, as such the reference marking R3 or the line R3should run parallel to the working direction AR. In order to prevent theoperator of the machine tool 10 from being irritated by this, theevaluation device 80 ensures correct orientation of an image of thedetection range EB2 and/or EB1 on the display device 25. The evaluationdevice 80 determines for example the orientation of the referencemarking R3 in relation to the X-axis XE and/or Y-axis YE and correctsthe orientation of the reference marking R3 so that it runs parallel tothe Y-axis YE. An image corrected in this way is shown by way of examplein the display device 25 in FIG. 3. Naturally, the evaluation device 80can in addition also carry out a rectification of such an image of andetection range EB1 or EB2 on the display device 25 so that for examplethe reference marking R1 and/or R2 are represented with lines runningparallel or at right angles to the reference marking R3. However, inFIG. 3 this rectification is only carried out for the reference markingR2, not for the reference marking R1. One can see the correspondinglydistorted representation of the reference marking R1 compared with thereference marking R2.

A further possibility for evaluating the reference markings R1 and/or R2is for example possible on the basis of stored images SR1 and SR2 of thereference marking R1 and R2. The evaluation device 80 can compare thestored images SR1 and SR2 with images AR1 and AR2 captured by the toolsensors 61, 62 in order in this way to determine one or more correctionvalues, to carry out a rectification or the like. For example, arectification function or rectification table determined forrectification of the so to speak real images AR1 and AR2 can be used bythe evaluation device 80 to rectify further images which are representedby the sensor signals from the tool sensors 61 and 62 and for exampleshow the work tool 15 or the like. The images SR1 and SR2 can forexample be stored as program code or stored information in an evaluationprogram 80A which can be executed by the processor 81 or, as illustratedin the drawing, stored in the memory 82. If stored in the memory 82 itis possible to load the images SR1 and SR2 into the memory 82 asparameter data.

An intrinsic calibration of the tool sensors 61, 62 is explained withreference to FIG. 28. The tool sensors 61, 62, which are for examplealready installed in the machine tool 10 can, with their detectionranges, register reference markings R11, R12, R13 and R14, for exampleif their detection range is directed through the opening of theenclosure device 21 for the work tool 15. In this case the machine tool10 is brought into several positions relative to the reference markingsR11-R14, wherein the evaluation device 80 registers the respectivereference markings R11-R14 and in particular their position anddistortion in space. The evaluation device 80 can then intrinsicallycalibrate the tool sensors 61, 62 or evaluate their tool sensor signalso to speak in an intrinsically calibrated manner.

In the drawing, the detection ranges EB1 and EB2 are substantiallyrepresented with respect to their orientation. The detection range EB2of the tool sensor 62 has a significantly narrower angle than thedetection range EB1. For example, the detection angle of the tool sensoris twice as wide or even greater than the detection range EB2 of thetool sensor 61.

That is to say the tool sensor 61 is so to speak a wide-angle sensor.The tool sensor 61 comprises so to speak a wide-angle camera.

This arrangement makes it possible that the tool sensor 62 not onlycovers the region in the direction of the front machined edge KV, butcan also for example detect and display a workpiece marking MA on theworkpiece W, as is indicated in the FIGS. 12 and 15. The workpiecemarking MA is omitted in the FIGS. 13, 14, 16 and 17 for reasons ofsimplification, but is nonetheless displayed by the display device 25.

The operator can orient himself on the workpiece marking MA, for examplelining up the target line SO1 with the workpiece marking MA, so that theposition of the front machined edge KV2 is optimally defined. However,an automatic or semi-automatic concept is also advantageous. Forexample, a difference information DI can be displayed on the displaydevice 25 which indicates a current distance between the actual machinededge, in particular the marking IST1 (FIG. 13) and the target machiningposition SO1 and/or the position of the workpiece marking MA. In thisway, the operator easily recognises the progress of work and can forexample reduce the rotational speed of the drive motor 13 and/or reducethe advance speed of the manually-operated machine tool 10 in relationto the workpiece W accordingly before reaching the front machined edgeKV1 and or the workpiece marking MA.

However, an automatic or semi-automatic concept is particularlyfavourable. For example, the evaluation device 80 controls the drivemotor 13 and/or an actuating drive 90 and/or a brake 90 in such a waythat the machining of the workpiece W ends on reaching, or beforereaching, the workpiece marking MA. For example, the evaluation device80 can, by means of the aforementioned image processing steps, inparticular an edge detection, grey value formation and the like, detectthe line of the marking MA. If the work tool 15 is in the location ofthe workpiece marking MA, i.e. the front machined edge KV1 reaches theworkpiece marking MA, the evaluation device 80 can for example shut offthe drive motor 13. Alternatively or in addition it is advantageous ifat the same time a brake 91 is activated by the evaluation device 80, sothat the tool 15 stops as quickly as possible. Moreover, in addition oralternatively, an actuation of an actuating drive 90 is also expedient,which the evaluation device 80 actuates for example in order to exchangethe work tool 15 or remove it from the workpiece W if the machined edgeKV reaches the workpiece marking MA.

The concept according to the invention, which has already beenexplained, can be realised not only in the case of mobile machines whichcan be moved or guided relative to the workpiece, but also in the caseof semi-stationary machines, for example in the case of a machine tool110. The machine tool 110 has a drive unit 111 with a drive motor 113which serves to drive a tool holder 14 for a work tool 115, for examplea saw blade. The drive unit 11 is adjustable relative to a machine base129 which can be placed on an underlying surface. For example, a guideelement 130, for example a rotary table, is mounted on the machine base129 so as to be rotatable around an axis A1. The axis A1 extendshorizontally in relation to a guide surface 132 of the guide element130. Furthermore, a tower-like structure 134 from which guide rails orguide elements 135 project is provided on the guide element 130. Theguide rails or guide elements 135 allow a longitudinal adjustment orsliding adjustment SL along a sliding axis A2, so that the saw blade orwork tool 115 can so to speak be moved in a linear manner along aworkpiece W resting on the guide surface 132.

In addition, the work unit 111 can be swivelled around a swivel axis A3,so that the work tool 115 penetrates into the workpiece to differentdepths.

The operator can for example grip the drive unit 11 by a handgrip 120and move it in relation to the guide element 130 in relation to one ormore of the axes A1-A3.

The machine tool 110 can also be provided with a display device 25 whichfor example displays sensor signals or tool sensor signals from toolsensors 161, 162 which are arranged on opposite sides of the work tool15, preferably within or beneath an enclosure device 121 for the worktool 15. Accordingly, actual machined edges or target machined edges canlikewise be displayed on the display device 25.

It is thereby possible that, in the case of an advance movement alongthe axis A2, first a rear image section generated by the tool sensor162, then a front image section generated by the tool sensor 161 aredisplayed on the display device 125. In this case a time condition isdecisive, i.e. for example such that on switching on the drive motor 113the image section generated or supplied by the tool sensor 162 is firstdisplayed on the display device 125.

The same principle is also advantageously applied in the case of themachine tool 10, so that image sections which are or can be generated onthe basis of the tool sensor signals from the tool sensors 61, 62 aredisplayed, for example controlled by a switchover device 84.

For example, the switchover device 84 comprises or is formed by acorresponding program module which contains program code which can beexecuted by the processor 81.

Furthermore, the switchover device 84 can determine, for example bymeans of the tilt sensor 65 and/or the acceleration sensor 66, whetherthe tool signal of the tool sensor 61 or the tool signal of the toolsensor 62 is to be displayed on the display device 25. Furthermore, theswitchover device 84 can for example display the tool signals from thetool sensors 61, 62 on the display device 25 according to a timecondition, for example in alternating succession at the beginning of anoperation, first displaying the tool signal of one tool sensor, thenthat of the other tool sensor or the like.

Finally, it is also advantageous if a manual operating element 76, forexample a pushbutton, a brightness sensor which can be operated by theoperator or the like is provided and/or configured to actuate theswitchover device 84 so as to switch between the tool signals of thetool sensors 61 and 62.

It should be mentioned at this point that the display device 25 can beequipped with or can be configured as a touch-sensitive display device,for example a so-called touchscreen. The operator can generate controlcommands for the machine tool 10 by selecting a predetermined field orregion of the display device 25 and/or through a predetermined operatinggesture, for example a swiping movement or the like. The operator canfor example generate a control signal for actuation of the switchoverdevice 84 on the display device 25, so that this displays, for examplesimultaneously, both tool signals from the tool sensors 61 and 62 oronly one of these.

When the work tool 15 cuts into the workpiece W, the tool sensor signalof the tool sensor 62 is preferably displayed first, in the event of asubsequent advance movement, which can be detected by the accelerationsensor 66 or also the tilt sensor 65 through a corresponding detectionof the depth adjustment position S1, S2 or the like, the tool sensorsignal of the tool sensor 61 is then displayed, so that the frontmachined edge is displayed to the operator. However, a time-basedcontrol is also possible such that when the machine tool 10 is put intooperation the signal of the tool sensor 62 is displayed first then,following a predetermined or adjustable time, the signal of the toolsensor 61.

Functions of a height measurement are explained in more detail in thefollowing with reference to the FIGS. 30-34. A height measurement hasgreat advantages in particular in connection with a display of anexpected machined edge, since it is advantageous if the work tool 15penetrates into the workpiece W to an optimal penetration depth, whereinthe height of the workpiece should be known for this purpose. Theoptimal penetration depth is adjustable on the depth adjustment device40 or adjustable by means of the actuating drive 90. If the machinededge or expected machined edge resulting from the respective depthadjustment or relative position of the drive unit 11 relative to theguide element 30 is then also displayed on the display device 25 or soto speak also automatically monitored in that for example the actuatingdrive 90 or the brake 91 is operated, a concept which is convenient forthe operator is achieved.

The height measurement of the machine tool 10 is explained in thefollowing in different variants:

A height measuring device 95 of the machine tool 10 uses for example therear tool sensor 62. It can be seen that the detection range of the toolsensor 62 is optimally directed at a rear end face of the workpiece W,viewed in the working direction, so that an upper workpiece edge WKO anda lower workpiece edge WKU lie within the detection range of the toolsensor 62. The machine tool 10 is thereby supported on the workpiece Wwith a large part of the guide surface 32, so that the correspondingheight measurement of the height measuring device 95 takes place underoptimal boundary conditions.

In connection with the height measurement, the image shown in FIG. 31 isfor example superimposed on the display or display device 25, in whichthe operator sees on the one hand the work tool 15, at least as anoutline, but preferably in real form, but on the other hand also atleast a partial image WT of the workpiece W, for example the end face WSas well as a partial section of the upper side of the workpiece WO andthe two workpiece edges WKU, WKO. In addition, the operator isexpediently displayed markings MO and MU for the upper workpiece edgeWKO and the lower workpiece edge WKU on the display device 25.

The height measurement by means of the height measuring device 95 cantake place in different ways:

In a first variant, the machine tool 10 is for example oriented suchthat the marking MO for the upper workpiece edge WKO is lined up withthe real displayed image of the workpiece W according to FIG. 13. Theheight measuring device 95 can then detect the lower workpiece edge WKU,for example on the basis of a contrast measurement or other suchmeasures, and superimposes the marking MU. It is thereby assumed that ameasuring angle MW at which the camera or the tool sensor 62 so to speakviews the upper workpiece edge WKO or at which the tool sensor 62 isoriented in relation to the upper workpiece edge WKO if the marking MOcoincides with the image of the workpiece W displayed in the image onthe display device 25. The measuring angle MW is provided between aparallel plane PL parallel to the guide surface 32 and a beam whichextends between the upper workpiece edge WKO and the tool sensor 62. Thesame angle MW is also present between a measuring plane ME and the endface WS of the workpiece W. There is thus a linear connection between aheight H, for example the height H1 in FIG. 32, and a distance dx1 inthe measuring plane ME, for example corresponding to a number of pixelson the display device 25. This becomes particularly clear through acomparison of FIGS. 32 and 33. In the case of the workpiece W1illustrated in FIG. 32, a height H1 is present which is manifested as adistance dx1 in the measuring plane ME. In contrast, in the case of theworkpiece W2, which has a height H2, a correspondingly shorter distancedx2, which is proportional to the height H2, is present between a beamextending between the tool sensor 62 and the lower workpiece edge WKUand the beam which is assigned to the upper workpiece edge WKO.

The respective workpiece height is expediently displayed on the displaydevice 25 as a height specification HI, in particular in numericalvalues. For example, in the case of the height specification HI in thedrawing, a height of the workpiece W of 47 mm is displayed.

According to an alternative measuring principle, the height measuringdevice 95 is first, or in a first step, oriented on the lower workpieceedge WKU in order to measure the height of the workpiece. This can forexample be effected in that the operator positions the machine tool 10correspondingly on the workpiece W or, in the case of an automaticmethod, in that in a first step the height measuring device 95 detectsthe lower workpiece edge WKU on a relative movement of machine tool 10and workpiece W.

The manual orientation of the machine tool 10 and of the workpiece W inrelation to the lower workpiece edge WKU has the advantage that theoperator can locate the as a rule difficult-to-detect lower workpieceedge WKU himself with his precise eye, because as a rule a lowercontrast is to be observed in the case of the lower workpiece edge WKU,namely between the workpiece and the environment.

In contrast, the height measuring device 95 has it easier, so to speak,when it comes to detecting the upper workpiece edge WKO. For example, ahigher contrast is to be observed in the region of the upper workpieceedge WKO. The contrast is for example created in that the workpiece edgeis illuminated from the machine tool 10, in particular by means of theillumination device 70. Furthermore, the height measuring device 95 canfilter out any wood grain or other transverse structures present on theworkpiece end face WS as non-valid structures which do not represent aworkpiece edge, because the so to speak last transverse contour beneaththe guide surface 32 can be unequivocally identified as the upperworkpiece edge.

However, in the case of this method there is no linear connection, butthe progression indicated in FIG. 34. Here, a pixel distance DPIXbetween the lower workpiece edge WKU and pixels representing the upperworkpiece edge are shown on the display device 25 in the case ofdifferent workpiece heights H1, H2, H3 as well as HMAX.

On this basis the evaluation device 80 can for example plot a curve DPIX(of H), i.e. a pixel distance depending on a workpiece height. Forexample, the operator sets down reference workpieces, one after another,on the guide surface 32 in order to determine the curve DPIX(H). Theheight measuring device can for example then superimpose on the displaydevice 25 the markings MO and MU analogous to the workpiece height.However, the curve DPIX (of H) is expediently already pre-programmed orotherwise stored.

However, instead of orienting the machine tool 10 with reference to theoptical marking MO it is also conceivable that the operator orients a soto speak mechanical or physical marking 96, for example a line markingon the guide element 30, on the upper workpiece edge WKO.

The aforementioned methods are so to speak static, i.e. the operatororients the machine tool 10 on the workpiece W in order to measure itsheight. Significantly simpler are the measures explained in thefollowing, in which the operator simply needs to move the machine tool10 and the workpiece W relative to one another and the height measuringdevice 95 so to speak automatically determines the height H of theworkpiece W.

For example, in the event of a relative adjustment of workpiece W andmachine tool 10, an optical image detection means on the machine tool 10can for example detect if the upper workpiece edge WKO or the lowerworkpiece edge WKU assume a reference position in relation to the toolsensor 62, for example the position illustrated in FIGS. 30, 32 and 33.An edge detection means is for example conceivable or possible for thispurpose. In this moment, the height measuring device 10 also determinesthe position of the other workpiece edge, i.e. the upper workpiece edgeWKO or the lower workpiece edge WKU, so that at the time of measurementboth workpiece edges WKO and WKU are detected by the height measuringdevice. It is possible that the height measuring device 35 so to speaktakes a snapshot of this reference situation, i.e. an image in whichboth workpiece edges WKU and WKO are visible if the reference position,for example the position illustrated in FIGS. 30, 32, and 33, is assumedduring the relative adjustment of workpiece W and machine tool 10.

A reference light source 68 can also be used to determine a respectivereference position. The reference light source 68 shines so to speakroughly parallel to the detection range of the tool sensor 62. If themachine tool 10 is still at a distance from the workpiece 10 (i.e. stillmoved to the left in FIG. 30) the light beam of the reference lightsource 68, for example a laser beam or laser pointer, is directed pastthe workpiece W. If the machine tool 10 is then moved forwards relativeto the workpiece W, for example into the position illustrated in FIG.30, the light from the reference light source 68 touches the lowerworkpiece edge WKU. The camera or the tool sensor 62 recognises thereflection on the lower workpiece edge WKU as a trigger signal, forexample in order to capture the image, already explained, in which thelower workpiece edge WKU and the upper workpiece edge WKO are visible.It is also possible that in this situation the tool sensor 62 or theheight measuring device 95 detects the upper workpiece edge WKO, throughimage recognition or other measures, in order ultimately to determinethe height H of the workpiece W from the information regarding the lowerworkpiece edge WKU and the upper workpiece edge WKO.

Such a procedure is indicated in FIG. 38. For example, the imagecaptured by the, viewed in the working direction, rear tool sensor 62 isillustrated in FIG. 38. For example, the machine tool 10 is moved overthe workpiece W along a movement direction BR1. A light reflection LR,which is generated by a reference light which is projected onto theworkpiece W by means of the reference light source 68, thereby so tospeak wanders from the lower workpiece edge WKU to the upper workpieceedge WKO and wanders so to speak along a path PL. Before the referencelight reaches the lower workpiece edge WKU it is virtually not reflectedby the environment of the workpiece W, which the tool sensor 62registers accordingly. If the reference light is moved over the upperworkpiece edge WKO, the light reflection LR remains fixed relative forexample to the work tool 15. The light reflection LR moves, on the onehand, with a movement component parallel to the movement direction BR1,but on the other hand also transversely thereto in a movement directionBR2. The height measuring device 95 can determine, for example on thebasis of the assignment function illustrated in FIG. 34, the height H ofthe workpiece W on the basis of the distance through which the lightreflection LR passes in relation to one or both of the movementdirections BR1, BR2, for example the distance DR2 in the movementdirection BR2.

Filters 362, 368 (FIG. 30), for example polarisation filters, colourfilters or the like, can be positioned in front of the tool sensor 62and/or the reference light source 68. Preferably, the filters 362, 368are matched to one another, so that for example the light from thereference light source 68 is limited by the filter 368 to apredetermined colour spectrum to which, due to the filter 362, the toolsensor 62 responds particularly sensitively or exclusively. It is alsopossible that the filter 368, as a polarisation filter, polarises thelight from the reference light source 68, i.e. allows it to pass in apredetermined orientation, and the filter 362, likewise as acorrespondingly oriented polarisation filter, only allows light with theorientation corresponding to the filtering by the filter 362 to pass tothe camera or to the tool sensor 62.

However, it is also advantageous if only one of the filters 362, 368 ispresent. For example, where the filter 362 is in the form of apolarisation filter, reflections or the like, in particular causedthrough the influence of extraneous light or due to the reference lightsource 68, can be filtered out. If the tool sensor 62 is particularlysensitive to a particular light colour, the filter 368 is for examplesufficient to limit a colour spectrum of the reference light source 68to this light colour.

A continuous determination of the workpiece height, namely in that alongitudinal distance of the tool sensor 62 and thus the heightmeasuring device 95 from the end face WS is registered, is for examplepossible by means of a distance sensor 67.

The distance sensor 67 is for example a laser sensor, an ultrasonicsensor or the like.

 10 machine tool  11 drive unit  12 machine housing  13 drive motor  14tool holder  15 work tool  16 saw blade  17 energy supply connectionmains cable  18 energy store/18B plug  19 handgrip, top  20 handgrip,front  21 enclosure device/protective cover for   15  22 dust extractionduct  23 extraction connection  24 cover for 21  25 display device (25) 26 display  27 operating element for drive switch  28 operating elementfor depth   adjustment device  29 stop for 40  30 guide element/sawbench  31 guide plate  32 guide surface  33 guide groove, guide rail  34 35 bearing arrangement  36 depth adjustment bearing  37 tiltbearing/mitre bearing  38 bearing elements of 37  39  40 depthadjustment device  41 mounting contour/guide  42 scale  43 stop element 44 fixing device  45 operating element  46  47  48  49  50 guide rail50A, guide device  51 upper side  52 guide projection for 33  53underside  54 narrow side of saw blade  55 upper edge of 54  56longitudinal end, front  57 longitudinal end, rear  58  59  60 sensorarrangement  61 tool sensor, front  62 tool sensor, rear  63 positionsensor, stop element  64 position sensor, depth adjustment   bearing  65tilt sensor  66 acceleration sensor  67 distance sensor  68 referencelight source  69 brightness sensor  70 illumination device  71 lightsource  72 light source  73 light source arrangement  74 diffusingelement for 71  75 diffusing element for 73  76 operating element  77 78  79  80 evaluation device  80A evaluation software  81 processor  82memory  83 assignment table, 83A assignment   function  84 switchoverdevice  85  86  87  88  90 actuating drive  91 brake  92  93  94  95height measuring device  96 mechanical marking  97  98  99 100 suctiondevice 101 suction hose 102 EB1 detection range 61 PB test region M1-measuring field M4 MA workpiece marking on workpiece DI differenceinformation MO marking, upper edge MU marking, lower edge OPToptimisation means WK1, partial workpiece contact regions WK2 AR1, imageR1, R2 AR2 SR1, stored image R1, R2 SR2 P particles PS particles flow TSdepth adjustment axis SA tilt axis/mitre axis AR working direction S0-2adjustment position Ex penetration depth SD sensor distance MW measuringangle ME measuring plane PL parallel plane d DPix pixel distance Wworkpiece, workpieces 1/2 WKU lower workpiece edge WKO upper workpieceedge WS end face of the workpiece WU underside of the workpiece WO upperside of the workpiece H workpiece height

1. A mobile machine machine tool for machining a workpiece, wherein themachine tool has an in particular plate-like guide element with a guidesurface for guiding the machine tool on the workpiece or the workpieceon the machine tool, wherein the machine tool has a drive unit with adrive motor for driving a tool holder arranged on the drive unit,wherein the machine tool is provided with a tool sensor arrangement fordetecting a workpiece contact region in which a work tool arranged onthe tool holder, in particular a cutting tool, is in contact with theworkpiece wherein the tool sensor arrangement comprises at least twotool sensors, the detection ranges of which are assigned to differentpartial workpiece contact regions of the workpiece contact region. 2.The mobile machine tool according to claim 1, wherein the work toolengages at least partially between the detection ranges of the toolsensors, so that the detection range of one tool sensor assigned to thepartial workpiece contact region is at least partially obstructed by thework tool so as to prevent registration by the other tool sensor.
 3. Themobile machine tool according to claim 1, wherein the detection rangesare assigned to opposite sides of the work tool and/or the partialworkpiece contact regions of the workpiece contact region are providedon opposite sides of the work tool.
 4. The mobile machine tool accordingto claim 1, further comprising several tool sensors, for detecting ineach case a partial workpiece contact region.
 5. The mobile machine toolaccording to claim 1, further comprising at least three tool sensorswhich are arranged in a row arrangement, wherein the row arrangementruns, in the geometry of an outer circumferential contour of the worktool, around its outer circumferential contour.
 6. The mobile machinetool according to claim 1, wherein one partial workpiece contact regioncorresponds to an entry region of the work tool in the workpiece and theother partial workpiece contact region corresponds to an exit region ofthe work tool from the workpiece.
 7. The mobile machine tool accordingto claim 1, wherein the tool holder is mounted adjustably relative tothe guide surface in order to adjust a penetration depth of the worktool in the workpiece, and wherein the tool sensors are arranged in theregion of a greatest distance of the partial workpiece contact regionsat the maximum penetration depth of the work tool in the workpiece. 8.The mobile machine tool according to claim 1, wherein at least one toolsensor is arranged on a side of the guide element facing away from theguide surface and/or on a side of the guide element assigned to thedrive unit.
 9. The mobile machine tool according to claim 1, wherein atleast one tool sensor, is arranged in a dust extraction region and/orbeneath a cover.
 10. The mobile machine tool according to claim 1,further comprising an illumination device for illuminating the workpiececontact region.
 11. The mobile machine tool according to claim 10,wherein for each partial workpiece contact region, the illuminationdevice has an illumination element for individual illumination of therespective partial workpiece contact region.
 12. The mobile machine toolaccording to claim 1, further comprising a display device for displayingsensor signals from the tool sensors.
 13. The mobile machine toolaccording to claim 1, further comprising a switchover device forswitching between the sensor signals of the tool sensors, wherein theswitchover device outputs the sensor signal of one tool sensor or thesensor signal of the other tool sensor as output signal in priority overthe in each case other sensor signal depending on at least one switchingcondition.
 14. The mobile machine tool according to claim 13, whereinthe at least one switching condition comprises or is formed by a timecondition and/or an acceleration signal and/or a switching signal of amanual operating element.
 15. The mobile machine tool according to claim13, wherein the switchover device is provided with a manually operableoperating element or a sensor, in order to switch between the sensorsignals from the tool sensors, or can be actuated through the operatingelement or the sensor in order to switch between the sensor signals fromthe tool sensors.
 16. The mobile machine tool according to claim 1,wherein at least one tool sensor is arranged on the guide element. 17.The mobile machine tool according to claim 1, wherein the detectionranges and/or optical axes of the tool sensors are arranged at differentangles relative to an outer circumference of the work tool.
 18. Themobile machine tool according to claim 1, wherein the detection rangesof the tool sensors have different detection angles.
 19. The mobilemachine tool according to claim 1, wherein the drive unit is, by meansof a bearing arrangement, mounted adjustably on the guide element inorder to adjust at least two adjustment positions of the tool holderrelative to the guide surface, wherein at least one adjustment positioncorresponds to a workpiece machining position in which the work toolarranged on the tool holder is, in the workpiece contact region, incontact with the workpiece.
 20. The mobile machine tool according toclaim 19, further comprising at least one tool sensor for detecting theworkpiece contact region and at least one position sensor, separate fromthe tool sensor, for detecting a relative position of the drive unitrelative to the guide element, and wherein the machine tool has anevaluation device for evaluating sensor signals of the position sensorand of the tool sensor.
 21. The mobile machine tool according to claim1, wherein the tool sensor is configured and/or aligned to detect aworkpiece marking arranged on the workpiece.
 22. The mobile machine toolaccording to claim 1, wherein the tool is configured to provide at leastone function depending on a detection of a workpiece marking arranged onthe workpiece.
 23. The mobile machine tool according to claim 22,wherein the at least one function comprises a display of a distance of acurrent machined edge from the workpiece marking and/or an actuation ofthe drive unit and/or a braking of the work tool and/or of an actuatingdrive of the machine tool in order to adjust the drive unit relative tothe guide unit on reaching the workpiece marking.